Heat-resistant resin container and method of producing the same

ABSTRACT

A container with a flange having excellent heat resistance and impact resistance in the lower part of the barrel portion and having excellent transparency in the wall despite the container is formed by molding an amorphous polyester sheet, and a method of producing the same.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. application Ser. No.10/628,246 filed Jul. 29, 2003, which is a Divisional Application ofU.S. application Ser. No. 09/959,955 filed Nov. 13, 2001, which is a 371of PCT Application No. PCT/JP01/01918 filed Mar. 12, 2001, and whichclaims priority based on Japanese Patent Application No. 303773/00 filedOct. 3, 2000 and Japanese Patent Application No. 2004-96477 filed Mar.29, 2004; the above-noted applications incorporated herein by referencein their entirety.

TECHNICAL FIELD

The present invention relates to a container with a flange obtained byheat-molding a sheet provided with a thermoplastic polyester layer, andto a method of producing the same. More specifically, the inventionrelates to a polyester container with a flange having improved impactresistance and heat resistance in the lower part of the barrel thereofand having superior transparency.

The invention further relates to a cup-like container with a flangehaving excellent stacking performance, and to a method of producing thesame.

BACKGROUND ART

Thermoplastic polyesters such as polyethylene terephthalate and the likehave excellent impact resistance, heat resistance and transparency aswell as a certain degree of gas barrier property, and have been widelyused for producing a variety of kinds of packaging containers.

Such packaging containers can be represented by a container with aflange obtained by molding a stretched or unstretched thermoplasticpolyester sheet.

Japanese Unexamined Patent Publication (Kokai) No. 53852/1984 disclosesa method of producing a transparent container by monoaxially stretchinga thermoplastic resin sheet while maintaining the reduction ratio of thewidth of the sheet to be not larger than 10% and heat-molding the thusobtained monoaxially oriented sheet (prior art 1).

Japanese Examined Patent Publication (Kokoku) No. 27850/1989 discloses amethod of heat-molding a polyester sheet by molding a biaxiallystretched polyester sheet having a crystallinity of not larger than 30%and an index of surface orientation of from 0.02 to 0.15 by utilizingthe compressed air along a mold heated at a temperature which is nothigher than the crystallizing temperature (Tc° C.) of the polyester butis not lower than (Tc-70)° C., heat-treating the obtained molded articleby bringing it into contact with the heated mold, fitting a cooling moldto the heating mold, the cooling mold having a shape nearlycorresponding to the heating mold, forcibly transferring the moldedarticle toward the cooling mold side from the heated mold side byblowing the compressed air, and cooling the molded article upon contactwith the cooling mold (prior art 2).

Japanese Examined Patent Publication (Kokoku) No. 36534/1992 discloses apolyester container having a heat-adhering portion that can be thermallyadhered to the closure member, the container being obtained by molding apolyester sheet containing a polyethylene terephthalate as a chiefconstituent component, the heat-adhering portion having a crystallinityof smaller than 20%, and the bottom portion and(or) the side portion ofthe container having the crystallinity of not smaller than 20%, thecontainer being useful as an ovenable tray (prior art 3).

Japanese Patent No. 2947486 discloses a method of producing a biaxiallystretched thermoplastic product by forming a biaxially stretchedintermediate product by blow-molding a sheet-like thermoplastic materialin a tube at a stretching temperature while preventing the material fromadhering to the top of the side walls, placing the intermediate producton a male mold of a preset size and a texture, heating the intermediateproduct and the mold at a temperature higher than the temperature forstretching the thermoplastic material so that the intermediate productis thermally shrunk on the surface of the mold, cooling the intermediateproduct that is thermally shrunk, and taking the thermally shrunkintermediate product out of the mold (prior art 4).

The prior art 1 uses a monoaxially stretched sheet as the sheet formolding. This molding method may be capable of improving thetransparency of the container but still leaves room for improvementconcerning the heat resistance of the container.

The prior art 2 uses a biaxially stretched sheet as the sheet formolding. This molding method may be capable of improving the heatresistance of the container but is not still satisfactory concerning theimpact resistance of the container.

These prior arts 1 and 2 use a sheet that has been stretched in advanceas the sheet to be molded and, hence, require a particular stretchingstep and, hence, an additional cost. It is therefore desired to use anunstretched sheet and to impart, in a step of forming the container, themolecular orientation that is desired from the standpoint of impartingthe container properties. It is further desired that the properties suchas heat resistance, impact resistance and transparency are imparted inthe steps of molding the container without requiring any particularstep.

According to the prior art 3, an amorphous polyester sheet that isheated and plasticized is formed into a tray by using a metal moldmaintained at a crystallizing temperature in order to heat-crystallizethe bottom portion and/or the side portion. However, there is nodisclosure concerning molecularly orienting the side portion bystretching, and it is considered that the container that is obtained isstill insufficient with respect to impact resistance and transparency.

The prior art 4 is to produce a final container by preparing a biaxiallystretched intermediate product by the blow-molding and by heat-shrinkingthe intermediate product on the male mold. This method, however,requires both heating for heat-shrinking the intermediate product on themale mold and cooling for shaping the heat-shrunk intermediate productand for taking it out. Therefore, this method is not still satisfactoryfrom the standpoint of thermal economy, extended periods of timeoccupying the molds and low productivity.

According to this production method, further, the remainder (so-calledskeleton portion) of the sheet after the container-forming portion iscut off occupies a considerable proportion, usually, 40 to 60% of thesheet. Namely, the remainder is wastefully discarded lowering the yieldof the material. It can be considered to reuse the remainder of thesheet by melting it deteriorating, however, the quality of the material.To avoid excess drop in the quality of the material, the sheet can beused only partly but not the whole of the remainder. To solve thisproblem, Japanese Unexamined Patent Publication (Kokai) No. 5-69478 andJapanese Examined Patent Publication (Kokoku) No. 7-67737 proposemethods of molding a cup-like thermoplastic resin container by forming apreform by the injection molding and, then, vacuum-molding or compressedair-molding the preform being assisted with a plug. According to themethod described in Japanese Unexamined Patent Publication (Kokai) No.5-69478, however, the theroplastic resin is not heat-set and, hence, theheat resistance is poor. According to the method described in JapaneseExamined Patent Publication (Kokoku) No. 7-67737, on the other hand, theheat resistance is imparted but extended periods of time are needed forthe heat-setting and for cooling the heat-molded container accompaniedby a problem of low production efficiency.

There has further been widely used a cup-like container made of athermoplastic resin having a flange, a cylindrical side wall hangingfrom the inner edge of the flange and a bottom wall closing the lowerend of the side wall. Prior to being filled with the content, thecup-like containers with a flange after molded are stacked in a pluralnumber by utilizing the flange portions. Usually, a plurality of thecup-like containers are stored or transported in a stacked state wherethe flange portion and the stacking portion which is a step formed onthe barrel of the container are engaged with each other (e.g., seeJapanese Unexamined Patent Publication (Kokai) No. 5-213358).

However, the cup-like container having the stacking portion is producedby a method by which a polyester sheet heated at a temperature higherthan a glass transition temperature is crystalled and press-stretched byusing a male plug and a female cavity heated at a temperature higherthan the glass transition temperature, the air pressure is applied tothe softened sheet, the softened sheet is moved from the male plug tothe female mold and is brought into contact with the female mold so asto be heat-set upon being heated to be not lower than the glasstransition temperature, the air pressure is released, and the sheet isshrunk back onto the male plug and is cooled. In this case, however, theflange portion which has been crystallized by heat or crystallized byorientation cannot be shrunk back, and the inner diameter of the mouthwhich is the inner peripheral diameter of the flange cannot be formed tobe sufficiently small with respect to the diameter of the step (stackingportion) formed relying upon the difference in the inner diameter of theplug barrel. As a result, the overlapping distance (=(outer stackingdiameter−inner diameter of the mouth)/2) becomes small between the uppercontainer and the lower container at the stacking portion in the stackedstate. Only about the thickness of the stacking portion can bemaintained as the overlapping distance at the greatest, and the stackingperformance becomes poor.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide acontainer with a flange exhibiting excellent heat resistance and impactresistance in the lower part of the barrel portion and excellenttransparency in the container wall despite it is obtained by molding anamorphous polyester sheet, and a method of producing the same.

Another object of the present invention is to provide a heat-resistantthermoplastic resin container having a novel profile of crystallinitiesin that the side wall portion of the container comprises orientedcrystals, and the outer surface of the side wall has a crystallinitylarger than that of the inner surface of the side wall, and a method ofproducing the same.

A further object of the present invention is to provide a method ofproducing a thermoplastic resin container, having split functions ofeffecting the heat-set by a female mold and effecting the cooling by aplug, shortening the time for occupying the mold and enhancing theproductivity.

A still further object of the present invention is to provide asheet-molded container having excellent heat resistance, impactresistance and transparency not only in the side wall of the containerbut also in the central portion on the bottom of the container despitethe container is obtained by molding an unoriented or amorphousthermoplastic polyester sheet, and a method of producing the same.

According to the present invention, there is provided an impactresistant container obtained by heat-molding a sheet provided with athermoplastic polyester layer comprising chiefly an ethyleneterephthalate unit, and having a flange portion, a barrel portion and aclosed bottom portion, the wall of the lower part of the barrel portionbeing oriented and crystallized so as to possess a crystallinity of notsmaller than 15% as measured by the density method, and the wall of thebarrel portion being oriented to satisfy the following formulas (1), (2)and (3),Iu(−110)/Iu(010)≦1.02   (1)IL(−110)/IL(010)≦0.89   (2)and(Iu(−110)/Iu(010))−(IL(−110)/IL(010))≧0.13   (3)

-   -   wherein Iu(−110) is a diffraction intensity of the surface        having an index of a plane of (−110) in the upper part of the        wall of the barrel portion of when an X-ray is incident on the        wall surface of the container perpendicularly thereto and when        the axial direction of the container is regarded to be a        perpendicular of the optical coordinate, Iu(010) is a        diffraction intensity of the surface having an index of a plane        of (010) in the upper part of the wall of the barrel portion of        when an X-ray is incident on the wall surface of the container        perpendicularly thereto and when the axial direction of the        container is regarded to be a perpendicular of the optical        coordinate, IL(−110) is a diffraction intensity of the surface        having an index of a plane of (−110) in the lower part of the        wall of the barrel portion of when an X-ray is incident on the        wall surface of the container perpendicularly thereto and when        the axial direction of the container is regarded to be a        perpendicular of the optical coordinate, and IL(010) is a        diffraction intensity of the surface having an index of a plane        of (010) in the upper part of the wall of the barrel portion of        when an X-ray is incident on the wall surface of the container        perpendicularly thereto and when the axial direction of the        container is regarded to be a perpendicular of the optical        coordinate,        as measured by the X-ray diffraction by using a curved PSPC        microdiffractometer.

In the container of the present invention, the ratio (H/R) of the height(H) of the barrel portion to the inner diameter (R) at the top of thebarrel portion is desirably in a range of from 0.8 to 2.0 for fulfillingthe object of the invention. Further, the flange portion may have acrystallinity of smaller than 10% as measured by the density method, orthe flange portion may have a crystallinity of not smaller than 20% asmeasured by the density method.

According to the present invention, there is further provided a methodof producing an impact resistant container by heating a sheet providedwith an amorphous thermoplastic polyester layer comprising chiefly anethylene terephthalate unit at a sheet temperature (Ts) that satisfiesthe following formula (4),Tg<Ts<Tg+50° C.   (4)

-   -   wherein Tg is a glass transition point of the thermoplastic        polyester,        and molding and heat-setting the sheet by using a plug having a        bottom area of not smaller than 70% of the bottom area of the        container and a plug temperature (Tp) that satisfies the        following formula (5),        Tg−30° C.<Tp≦Tg+30° C.   (5)        wherein Tg is the glass transition point of the thermoplastic        polyester,        in one step or in two steps in a metal mold with a plug-assisted        compressed air or vacuum.

In the production method of the present invention, it is desired thatthe metal mold has a temperature (Tm) that satisfies the followingformula (6),Tg≦Tm   (6)

-   -   wherein Tg is a glass transition point of the thermoplastic        polyester.

Further, the plug may be an ordinary plug or a plug having a steppedshoulder for forming a flange.

According to the present invention, further, there is provided aheat-resistant resin container obtained by molding a thermoplasticpolyester sheet, at least the side wall of the container being orientedand crystallized due to stretching, and the side wall of the containerhaving a crystallinity which is larger in the outer surface thereof thanin the inner surface thereof.

In the heat-resistant resin container of the present invention, it isdesired that:

-   -   1. The container has a flange portion, a side wall portion and a        bottom portion, and the ratio (H/D) of the height (H) of the        container to the diameter (D) of the container is not smaller        than 0.5;    -   2. The flange portion of the container is cloudy and the side        wall is transparent when it contains no pigment; and    -   3. A change in the volume of the container is not larger than        1.0% after it is heat-treated in an oven at such a temperature        that the side wall portion thereof is maintained at 90° C. for 3        minutes.

According to the present invention, further, there is provided a methodof producing a heat-resistant resin container by molding a thermoplasticresin sheet into the shape of a female mold heated at a temperaturehigher than the crystallization temperature of the resin by thecompressed air, followed by heat-setting and, then, reducing thepressure in the molded article so that the molded article shrinks intothe shape of a plug having the shape of a final container to impart theshape thereto, followed by cooling.

In the method of producing the heat-resistant resin container of thepresent invention, it is desired that:

-   -   1. A primary molded article obtained by stretching the        thermoplastic resin sheet by using a plug is molded with the        compressed air;    -   2. The thermoplastic resin sheet is an amorphous sheet of a        thermoplastic polyester;    -   3. The plug has a surface area wider by more than three times        than the area to be molded of the thermoplastic resin sheet; and    -   4. The temperature of the plug is not lower than the glass        transition point of the thermoplastic resin but is lower than        the temperature of the female mold.

The method of producing the heat-resistant resin container of thepresent invention can be put into practice even by a one-step moldingmethod or by a two-step molding method.

In the two-step molding method, it is desired that the thermoplasticresin sheet is stretched and molded by using a plug for stretch-moldingprior to applying the compressed air, and the obtained primary moldedarticle is supported by a shape-imparting plug in a separate step toeffect the molding with the compressed air and the shrinking. In thiscase, further, it is desired that the temperature of the shape-impartingplug is not higher than the glass transition point of the thermoplasticresin.

According to a second embodiment of the invention, the sheet may bestretched by using a stretching rod in either the one-step molding orthe two-step molding, and the obtained primary molded article may bemolded with the compressed air. In this case, the temperature formolding the plug can be selected to be from near room temperature to nothigher than the crystallization initiating temperature of thethermoplastic resin.

Further, the thermoplastic resin sheet that is used may have been shapedin advance so as to form the main heat-molding portion and the flangeportion. It is further desired the thermoplastic resin sheet iscrystallized at a portion that becomes the flange portion by beingclamped by a jig and that the flange portion is thickened or iscrystallized.

According to this method, further, at a position of the plugcorresponding to the container barrel, there are formed, on thecontainer, a bead portion that protrudes inward of the container and astacking portion located under the bead portion, to form a cup-likecontainer having excellent stacking performance.

According to the method of producing the cup-like container havingexcellent stacking performance, there is provided a heat-resistantcup-like container having excellent stacking performance forming thebead portion on the container barrel so as to protrude inwardly of thecontainer and the stacking portion at a position under the bead portion.It is desired that the bead is formed entirely or being divided into aplurality of portions in the circumferential direction of the barrel.

According to the present invention, further, there is provided a methodof producing a heat-resistant container by preparing an intermediatearticle by heat-shrinking a pre-molded article obtained bysolid-phase-molding the sheet provided with an amorphous thermoplasticpolyester layer, molding the intermediate product with the compressedair in a female metal mold for final molding heated at a temperaturehigher than the crystallization start temperature of said polyester,heat-setting the molded article, reducing the pressure inside the moldedarticle so that the molded article shrinks along the outer surface ofthe plug having the shape of the final container to impart the shapethereto, followed by cooling.

In the embodiment of the present invention, it is desired that the sheetis solid-phase-molded by pressing the sheet by using a plug forpre-molding, the sheet being clamped by a clamping metal mold and afemale mold for pre-molding, and by supplying the pressurized gas tobetween the sheet and the plug. In molding the sheet in this case, it isdesired that the sheet temperature is maintained to lie between theglass transition point (Tg) of the thermoplastic polyester +15° C. andthe glass transition point +40° C., that the plug is maintained at atemperature between the glass transition point −30° C. and the glasstransition point +20° C., and that the female mold for pre-molding ismaintained at a temperature between the glass transition point of thethermoplastic polyester +10° C. and the glass transition point +50° C.

In the present invention, further, it is desired that the pre-moldedarticle is supported by a plug for intermediate molding and is insertedin the female mold for intermediate molding, and the molded article iscaused to shrink along the outer surface of the plug to impart the shapethereto followed by cooling. In this case, it is desired that the femalemold for intermediate molding is maintained at a temperature in a rangeof not lower than the crystallization start temperature, that the plugfor intermediate molding is maintained at a temperature lower than thetemperature of the female mold for intermediate molding and in a rangeof from 80 to 110° C., and that the surface area of the pre-moldedarticle is from 1.1 to 1.5 times as large as the surface area of theintermediate article.

According to the present invention, further, it is desired that thefemale mold for final molding is maintained at a temperature of notlower than the crystallization start temperature of the thermoplasticpolyester, and that the plug for the final container is maintained at atemperature in a range of from the glass transition point of thethermoplastic polyester −20° C. to the glass transition point +20° C.

According to the present invention, there is further provided acontainer having excellent heat resistance and impact resistanceobtained by stretching and molding a thermoplastic polyester, thethermoplastic polyester in the bottom portion of the container having acrystallinity of not smaller than 15%, and the center in the bottomportion of the container being substantially transparent and having adistinguished diffraction peak in the surface of an index of a plane(010) in the X-ray diffraction.

In the container of the present invention, it is desired that:

-   -   1. The oriented crystallization tendency (U) as defined by the        following formula (I),        U=H(010)/H(−110)   (I)    -   wherein H(010) is a diffraction intensity of the surface having        an index of a plane (010) in the X-ray diffraction, and H(−110)        is a diffraction intensity of the surface having an index of a        plane (−110) in the X-ray diffraction,        is not smaller than 1.3 at the center in the bottom portion;    -   2. The sheet having the thermoplastic polyester layer is        stretched and molded in the solid phase; and    -   3. The crystallinity of the thermoplastic polyester in the side        wall of the container is not smaller than 15%.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating the principle of X-ray diffraction byusing a curved PSPC microdifractometer;

FIG. 2 is a diagram of X-ray diffraction of a barrel portion of acontainer according to the present invention;

FIG. 3 is a diagram illustrating the crystal lattice of a polyethyleneterephthalate;

FIG. 4 is a diagram of X-ray diffraction of a crystalline polyethyleneterephthalate;

FIG. 5 is a graph illustrating a relationship between the temperature ofa metal mold and the ratio of peak intensities;

FIG. 6 is a sectional view illustrating a container of the presentinvention together with a plug and a metal mold that are used;

FIG. 7 is a sectional view of a laminated sheet used in the presentinvention;

FIG. 8 is a side sectional view illustrating a step of supplying athermoplastic resin sheet in a one-step molding method;

FIG. 9 is a side sectional view illustrating a step of clamping andpre-stretching the thermoplastic resin sheet in the one-step moldingmethod;

FIG. 10 is a side sectional view illustrating a step of stretching thethermoplastic resin sheet in the one-step molding method;

FIG. 11 is a side sectional view illustrating a step of compressedair-molding and heat-setting into a secondary mold in the one-stepmolding method;

FIG. 12 is a side sectional view illustrating a step of shrinking,shaping and cooling a tertiary molded article in the one-step moldingmethod;

FIG. 13 is a side sectional view illustrating a step of parting thetertiary molded article in the one-step molding method;

FIG. 14 is a side sectional view illustrating a step of supplying thethermoplastic resin sheet in a first step in a two-step molding method;

FIG. 15 is a side sectional view illustrating a step of compressedair-molding the primary molded article into the secondary molded articlein the first step in the two-step molding method;

FIG. 16 is a side sectional view illustrating a step of parting thesecondary molded article in the first step in the two-step moldingmethod;

FIG. 17 is a side sectional view illustrating a step of inserting thesecondary molded article in the metal mold in the second step in thetwo-step molding method;

FIG. 18 is a side sectional view illustrating a step of compressedair-molding and heat-setting the secondary molded article in the secondstep in the two-step molding method;

FIG. 19 is a side sectional view illustrating portions of measurement ofthe containers of Examples 6 to 8 and Comparative Example 7 that will bedescribed later;

FIG. 20 is a side sectional view illustrating a step of clamping thesheet in the first-step molding (into a pre-molded article);

FIG. 21 is a side sectional view illustrating a step of stretching andshaping the sheet in the first molding step;

FIG. 22 is a side sectional view illustrating the pre-molded articlemolded in the first molding step;

FIG. 23 is a side sectional view illustrating a step of inserting thearticle in the metal mold in the second molding step (for molding anintermediate article);

FIG. 24 is a side sectional view illustrating a step of heat-shrinkingin the second molding step;

FIG. 25 is a side sectional view illustrating a step of cooling andshaping in the second molding step;

FIG. 26 is a side sectional view illustrating an intermediate articlemolded in the second molding step;

FIG. 27 is a side sectional view illustrating a step of inserting thearticle in the metal mold in a third molding step (into a finally moldedarticle);

FIG. 28 is a side sectional view illustrating a step of heat-setting inthe third molding step;

FIG. 29 is a side sectional view illustrating a step of shrinking andshaping in the third molding step;

FIG. 30 is a side sectional view illustrating a step of parting thefinally molded article formed in the third molding step;

FIG. 31 is a view illustrating an X-ray diffraction image at the centerof bottom of the container according to another embodiment of thepresent invention;

FIG. 32 is a side sectional view illustrating, partly on an enlargedscale, a state where conventional cup-like containers are stacked;

FIG. 33 is a side sectional view illustrating, partly on an enlargedscale, a state where the cup-like containers of the present inventionare stacked;

FIG. 34 is a side sectional view illustrating, partly on an enlargedscale, a step of heat-molding a conventional cup-like container;

FIG. 35 is a side sectional view illustrating, partly on an enlargedscale, a step of heat-molding a cup-like container of the presentinvention;

FIG. 36 is a sectional view illustrating a molding precursor used forthe present invention;

FIG. 37 is a sectional view illustrating a state where a preformed sheet(molding precursor) is fed to the heat-molding apparatus according to apreferred embodiment of the production method of the present invention;

FIG. 38 is a sectional view illustrating a manner of press-stretchingthe flange portion of the molding precursor in the heat-moldingapparatus of FIG. 37;

FIG. 39 is a sectional view illustrating a manner of stretching the mainheat-molding portion of the molding precursor by using a stretching rodin the heat-molding apparatus of FIG. 37;

FIG. 40 is a sectional view illustrating a manner of blow-molding themain heat-molding portion of the molding precursor in the heat-moldingapparatus of FIG. 37;

FIG. 41 is a sectional view illustrating a manner of shrinking back themain heat-molding portion of the molding precursor in the heat-moldingapparatus of FIG. 37;

FIG. 42 is a sectional view illustrating a completed container afterhaving trimmed the flange;

FIG. 43 is a view illustrating a method of selective crystallization byorientation for selectively crystallizing the flange portion;

FIG. 44 is a view illustrating a method of selective crystallization byheating for selectively crystallizing the flange portion (selectiveheating by the radiant heat); and

FIG. 45 is a view illustrating portions for measuring the sizes of themolding tools used in the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

A container according to a first embodiment of the present invention isobtained by heat-molding a sheet provided with a thermoplastic polyesterlayer comprising chiefly an ethylene terephthalate unit, and having aflange portion, a barrel portion and a closed bottom portion, the wallof the lower part of the barrel portion being oriented and crystallizedso as to possess a crystallinity of not smaller than 15% as measured bythe density method, and the wall of the barrel portion being oriented tosatisfy the above-mentioned formulas (1), (2) and (3) as measured byX-ray diffraction based upon the transmission method.

Referring to FIG. 1 illustrating the X-ray diffraction method used inthis invention, the samples to be measured are cut out from the lowerpart (sample is cut about a center which is 10 mm above the bottom) andfrom the upper part (sample is cut about a center which is 15 mm belowthe flange) of the barrel portion of the heat-molded container, and aremounted in a sample holder of a curved PSPC (position sensitiveproportional counter) microdiffractometer (PSPC-MDG) in a manner thatthe X-ray is perpendicularly incident on the container wall surface andthat the axial direction of the container is in agreement with theoptically vertical direction of the device. The X-ray is converged by acollimator into a fine beam, caused to be incident on the surface of thesample perpendicularly thereto, and the position (2θ) of the diffractedline and the intensity thereof are recorded on the PSPC.

FIG. 2 shows an X-ray diffraction image of the upper part and the lowerpart of the barrel portion of the container of the present inventionmeasured as described above.

In general, it has been known that the crystalline structure of thepolyethylene terephthalate is of the triclinic system having thefollowing lattice constants; i.e.,

-   -   a=4.56 angstroms    -   b=5.94 angstroms    -   c=10.75 angstroms    -   α=98.5°    -   β=118°    -   γ=112°

Referring to FIG. 3 illustrating the atomic arrangement of crystal unitlattice of a polyethylene terephthalate, the molecular chains of thepolyethylene terephthalate are extending in the direction of c-axis andare positioned at the ridgelines in the direction of c-axis, and a planeincluding a benzene ring is nearly along the surface of an index of aplane (100).

In the measurement of the above-mentioned PSPC-MDG in connection withthe crystalline polyethylene terephthalate (PET), diffraction peaksappear conspicuously on the surfaces having, generally, indexes ofplanes (010), (−110), (100) and (105). Relationships between the planes(hkl) of the crystal unit lattices and the diffraction angle 2θ are astabulated below, (h, k, l) 2 θ (010) 16° to 18° (−110)  22° to 24° (100)26° to 27° (105) 42° to 45°

FIG. 4 is a diagram of X-ray diffraction image of a barrel portion of acrystalline polyethylene terephthalate container by using the PSPC-MDG,and in which are clearly appearing diffraction peaks of the surfaceshaving the above-mentioned indexes of planes (010), (−110), (100) and(105).

When the X-ray diffraction image of the barrel portion of the PETcontainer of the present invention shown in FIG. 2 is compared with theX-ray diffraction image of the crystalline PET shown in FIG. 4,diffraction peaks are conspicuously appearing on the surfaces havingindexes of planes (010) and (−110) in the case of the barrel portion ofthe container of the present invention, whereas diffraction peaks aredisappearing on the surface having the index of a plane (100).

Further, when the X-ray diffraction image of the upper part of thebarrel portion of the container in FIG. 2 is compared with the X-raydiffraction image of the lower part of the barrel portion of thecontainer, it is obvious that the diffraction peak intensity of thesurface having the index of a plane (−110) is decreasing in the lowerpart of the barrel portion compared to the upper part of the barrelportion while the diffraction peak intensity of the index of a plane(010) is increasing.

In the PET crystals, it was pointed out already that the plane includingthe benzene ring is nearly in line with the surface having the index ofa plane (100). Here, however, the surface having the index of a plane(010) is at right angles with the benzene plane, X-axis and Y-axis.

In the barrel portion of the container of the present invention, theX-ray diffraction image shown in FIG. 2 is conspicuous, i.e., thediffraction peaks are conspicuous on the surfaces of the indexes ofplanes (010) and (−110), whereas the diffraction peaks are extinguishingin the X-ray diffraction image of the surface of the index of a plane(100), from which it is reasonable to consider that, in the barrelportion of the container, the benzene plane is arranged in parallel withthe wall surface of the barrel portion of the container.

That is, in the X-ray diffraction method, if the benzene plane is nearlyin parallel with the surface of the sample sheet, the diffraction on theplane (100) is not measured but the diffraction is measured on the plane(010) which is nearly perpendicular thereto. A large diffraction peakintensity on the plane (010) means that the benzene plane of a unit ofethylene terephthalate is in parallel with the surface of the sheet.Conversely, a large diffraction peak intensity on the plane (100) meansthat the benzene plane of a unit of ethylene terephthalate is inclinedwith respect to the film surface and is not in parallel therewith.

The ratio Iu(−110)/Iu(010) and the ratio IL(−110)/IL(010) in theabove-mentioned formulas (1), (2) and (3) represent, in a standardizedmanner, the degrees of parallelism between the benzene plane of PET andthe wall surface of the barrel portion at the upper and lower parts ofthe barrel portion of the container. The ratios become small when thedegree of parallelism is large and becomes large when the degree ofparallelism is small.

In biaxially stretching the polyethylene terephthalate containing aplane a phenylene group in the molecular chains thereof, however, it hasbeen known that the plane of the phenylene group is arranged in parallelwith the film surface (see, for example, Journal of the Academy ofFibers, Vol. 33, No. 10, 1977).

The container of the present invention, therefore, is biaxially orienteddespite it is formed by heat-molding the polyethylene terephthalatesheet, and the degree of the biaxial orientation is increasing in thelower part of the barrel portion, which is quite an unexpected fact.

In the present invention it is important that the ratio Iu(−110)/Iu(010)and the ratio IL(−110)/IL(010) lie in the ranges satisfying theabove-mentioned formulas (1), (2) and (3) from the standpoint ofaccomplishing the impact resistance, heat resistance and transparency.If all of them are not satisfied, both the impact resistance and theheat resistance become inferior as demonstrated in Comparative Examples1 to 5 appearing later.

In the present invention, it is desired that the ratio Iu(−110)/Iu(010)is not larger than 1.02 and, most desirably, not larger than 1.0. It isfurther desired that the ratio IL(−110)/IL(010) is not larger than 0.89and, most desirably, not larger than 0.7.

It is further desired that the difference between the ratioIu(−110)/Iu(010) and the ratio IL(−110)/IL(010) is not smaller than 0.13and, particularly, not smaller than 0.20.

In the container of the present invention, it is desired that the wallat the lower part of the barrel portion has a crystallinity of notsmaller than 15% and, particularly, not smaller than 17% as measured bythe density method.

In this specification, the crystallinity stands for the density methodcrystallinity (Xcv) expressed by the following formula,${Xc} = {\frac{\rho\quad c \times \left( {\rho - {\rho\quad a}} \right)}{\rho \times \left( {{\rho\quad c} - {\rho\quad a}} \right)} \times 100}$

-   -   wherein ρ is a density (g/cm³, 25° C.) of the sample measured by        using a density-gradient tube, ρa is a density of a perfectly        amorphous substance and is, generally, 1.335 g/cm³ in the case        of the PET, ρc is a density of a perfect crystal and is,        generally, 1.455 g/cm³ in the case of the PET, and Xcv is a        crystallinity (%).

When the crystallinity is not larger than 15%, the container exhibits adecreased heat resistance and cannot be used for hot-packaging thecontent.

In the container with a flange of the present invention, the flangeportion may have any crystallinity. In one embodiment, the flangeportion may have a crystallinity of smaller than 10% as measured by thedensity method. The flange portion having such a low crystallinityexhibits excellent heat-adhesiveness to the closure member. In anotherembodiment, the flange portion is so oriented and crystallized as topossess a crystallinity of not smaller than 20% as measured by thedensity method. The flange portion having such a high degree ofcrystallinity exhibits excellent mechanical properties and thermalstability.

A container according to the first embodiment of the present inventionis obtained by heating a sheet provided with an amorphous thermoplasticpolyester layer comprising chiefly an ethylene terephthalate unit at asheet temperature (Ts) that satisfies the following formula (4),Tg<Ts<Tg+50° C.   (4)

-   -   wherein Tg is a glass transition point of the thermoplastic        polyester,        and molding the sheet by using a plug having a bottom area of        not smaller than 70% of the bottom area of the container and a        plug temperature (Tp) that satisfies the following formula (5),        Tg−30° C.<Tp≦Tg+30° C.   (5)    -   wherein Tg is the glass transition point of the thermoplastic        polyester,        in one step or two steps in a metal mold with a plug-assisted        compressed air or vacuum, followed by heat-setting.

In the container of the present invention, the lower part of the barrelportion has preferentially been oriented biaxially as pointed outalready. To form the container having such a profile of orientation, itwas learned that the sheet temperature (Ts) and the plug temperature(Tp) must be maintained in suitable ranges in executing the molding withthe plug-assisted compressed air or vacuum and, besides, the plug musthave a proper shape.

That is, in effecting the molding with the plug-assisted compressed airor vacuum, the sheet is stretched onto the plug in the axial directionof the container and, hence, the wall of the barrel portion is chieflymonoaxially oriented. It is, however, important that the lower part ofthe barrel portion of the container of the present invention isbiaxially oriented. This can be effectively done by pulling the sheetthat is molded while supporting it on the plug and, particularly, bypulling the polyester of a portion of a small diameter on the bottom ofthe plug up to a barrel portion of the plug having a large diameter.

For this purpose, the sheet must be heated at a sheet temperature (Ts)that satisfies the above-mentioned formula (4), and the plug temperature(Tp), too, must satisfy the above-mentioned formula (5).

When the sheet temperature (Ts) exceeds the range of the formula (4)(seeComparative Example 1 appearing later), it becomes difficult toaccomplish the orientation profile structure defined by the invention,and the container exhibits inferior impact resistance and inferior heatresistance.

When the sheet temperature (Ts) becomes lower than the range of theformula (4), the polyester is not plasticized to a sufficient degree andcannot be stretch-molded into a container.

Further, when the plug temperature (Tp) exceeds the range of the formula(5)(see Comparative Example 2 appearing later), it becomes difficult toaccomplish the orientation profile structure defined by the invention,and the container exhibits inferior impact resistance and inferior heatresistance.

When the plug temperature (Tp) becomes lower than the range of theformula (5), the polyester sheet remains cold and cannot bestretch-molded into the container.

In the present invention, it is important to use the plug having abottom area which is not smaller than 70% and, preferably, not smallerthan 80% of the bottom area of the container in molding the sheet withthe plug-assisted compressed air or vacuum, from the standpoint ofimparting the orientation profile to the barrel portion.

When the bottom area of the plug becomes smaller than 70%, it becomesdifficult to accomplish the orientation profile structure defined by thepresent invention, either, and the container exhibits inferior impactresistance and inferior heat resistance as demonstrated in ComparativeExample 3 appearing later.

This is presumably due to that when the plug has a large bottom area,the polyester that is stretched up to the barrel portion of the plugremains in a sufficiently large amount in the bottom of the plugcontributing to increasing the biaxial orientation due to the stretchingin the axial direction and in the circumferential direction.

In the present invention, the molding with the plug-assisted compressedair or in vacuum and the heat-setting can be conducted in one step or intwo steps.

In the one-step method, a metal mold is heated at a heat-settingtemperature, the plug is advanced in the metal mold to draw the sheet,and the sheet that is drawn with the compressed air or in vacuum isinflated and is brought into contact with the metal mold to heat-set thebarrel portion.

A two-step method, on the other hand, uses a metal mold that is cooledand a metal mold that is heated at a heat-setting temperature, whereinthe plug is advanced in the metal mold that is cooled to draw the sheet,the sheet that is drawn with the compressed air or in vacuum is inflatedto prepare a pre-molded article which is then put into the metal moldthat is heated and is further inflated with the compressed air or invacuum, and is brought into contact with the metal mold to heat-set thebarrel portion.

In the present invention, it is desired that the metal mold used for theheat-setting has a metal mold temperature (Tm) that satisfies theabove-mentioned formula (6).

FIG. 5 illustrates a relationship between the metal mold temperature(Tm) and the ratio of peak intensities (I(−110)/I(010)), from which itis learned that confining the metal mold temperature (Tm) in the rangeof the formula (6) is still effective in placing the profile oforientation within the range of the invention.

In the present invention, the container with a flange which is amorphousor lowly crystalline can be produced by the plug-assisted molding byholding a portion that becomes a flange by a clamp. On the other hand,the container with a flange which is oriented and crystallized can beproduced by using a plug having a shoulder portion for forming flange,stretching even a portion that becomes a flange in a majority portion ofthe step of advancing the plug, and tightening the portion that becomesthe flange between the shoulder portion and the metal mold in the lastperiod of the step of advancing the plug.

Referring to FIG. 6 which illustrates the container of the presentinvention together with the plug and the metal mold, the container 1 isproduced by drawing the polyester sheet 2 by using the plug 3, inflatingthe polyester sheet 2 by the compressed air or vacuum in the metal mold,and bringing the wall of the container into contact with the metal moldso as to be heat-set.

The container 1 includes a flange portion 11, a barrel portion 12 and aclosed bottom portion 13, the barrel portion 12 having crystallinity andoriention properties as described above.

It is desired that the container has a ratio (H/R) of the height (H) ofthe barrel portion 12 to the diameter (R) thereof of, generally, notsmaller than 0.8 and, particularly, in a range of from 1.0 to 2.0.

In molding the sheet, the plastic sheet is heated at the above-mentionedsheet temperature (Ts). The plastic sheet is heated by using infraredrays or far infrared rays, by using a hot air furnace or by theconduction of heat.

The plug and the metal mold are maintained at the above-mentioned plugtemperature (Tp) and at the metal mold temperature (Tm). Thesetemperatures are controlled by turning on/off the heaters incorporatedin the plug and in the metal mold, or by passing a heat medium throughthe plug and the metal mold to control the temperature.

It was pointed out already that the plug used for the present inventionshould have a bottom area of not smaller than 70% of the bottom area ofthe container. It is, however, desired that the end of the barrelportion of the plug, i.e., a portion that is continuous to the bottomportion is forming a tapered portion 31 of which the diameter graduallyincreases toward the upper side as shown in FIG. 6. That is, uponforming such a tapered portion 31, it is allowed to easily draw thepolyester on the bottom portion of the plug onto the barrel portion, toproduce the container 1 having a good orientation profile.

It is desired that the tapered angle (α) of the tapered portion 31 isfrom 0.5 to 10° and, particularly, from 2 to 6° and that the taperedportion 31 is formed at a ratio of from 0.3 to 0.9 times of the heightof the plug.

In the embodiment shown in FIG. 6, further, the plug 3 has aflange-molding portion 32 so as to form a flange portion 11 that isoriented and crystallized.

The pressure applied to the sheet that is being molded may be thecompressed air from the plug side or may be the vacuum from the metalmold side, or may be a combination thereof. In general, the pressurehaving a magnitude of from 2 to 10 kg/cm² is applied from the side ofthe inner surface of the sheet.

Second Embodiment

According to the method of producing a heat-resistant resin container ofthe present invention, a thermoplastic resin sheet is molded, by thecompressed air, into the shape of a female mold that is heated to behigher than the crystallization temperature of the resin and is heat-setand, then, the pressure in the metal mold is decreased permitting themolded article to shrink to the shape of the plug which is of the shapeof a final container, thereby to impart the shape and cool.

The plug used in the present invention has the shape and size inagreement with the shape and size of inner surfaces of the finalcontainer, whereas the female mold has the shape and size larger thanthe shape and size of outer surfaces of the final container. The plugand the female mold are arranged in concentric in such a manner thatthey bite each other and separate away from each other. Further, aclearance (in the radial direction and in the axial direction) is formedbetween the outer surface of the plug and the inner surface of thefemale mold to permit the inflation of the thermoplastic resin beingmolded by the compressed air from the inner side and to permit theshrinkage thereof due to a decrease in the pressure from the inner side.

The plug used in the present invention works to stretch-mold the resinsheet into a molded article (primary molded article) which is inagreement with the outer surface of the plug and to shrink-mold theresin sheet into a final molded article (tertiary molded article). Inthe one-step molding method, the primary molded article and the tertiarymolded article have nearly the same shapes and sizes. In the two-stepmolding method, the primary molded article and the tertiary moldedarticle may have the same or different shapes and sizes. On the otherhand, the female mold used in the invention is to mold the primarymolded article into a secondary molded article of a size larger than theprimary molded article.

In the present invention, a feature resides in that the female mold isheated to heat-set the secondary molded article that is molded by thecompressed air, the plug is cooled to impart the shape to the tertiarymolded article that has shrunk due to a reduction in the pressure and toremove it out, and the functions are separately effected, i.e., thefemale mold effects the heating and the plug effects the cooling.

According to the production method of the present invention, therefore,the female mold is only heated while the plug is only cooled, and themolded article needs stay in the metal mold for a very shortened periodof time contributing to improving the productivity as compared to whenthe plug and the metal mold are heated and cooled alternately.

The primary molded article obtained by the stretch-molding beingassisted by the plug is further smoothly molded into the secondarymolded article by using the compressed air from the inside of theprimary molded article (i.e., from the inside of the plug). Moreover,the secondary molded article that is heat-set, is smoothly shrink-moldedinto a final container (tertiary molded article) by reducing thepressure from inside the secondary molded article (i.e., from inside theplug). Thus, the molding operation by using the female mold and themolding operation by using the plug are very smoothly carried out incooperation without at all wasting the time.

According to the present invention, the molding operation can be putinto practice by either the one-step method or the two-step methodwithout departing from the above-mentioned spirit and scope of theinvention. The one-step molding method is conducted through thefollowing steps by using a pair of plugs in combination with the femalemold; i.e.,

-   -   {circle over (1)} stretch-molding into a primary molded article        by using the plug;    -   {circle over (2)} molding the primary molded article into a        secondary molded article using the compressed air;    -   {circle over (3)} heat-setting the secondary molded article by        using the female mold;    -   {circle over (4)} shrink-molding the heat-set secondary molded        article into a tertiary molded article by reducing the pressure;        and    -   {circle over (5)} cooling the tertiary molded article by using        the plug.

The two-step molding method is the same as the one-step molding methodwith respect to that the above-mentioned basic steps {circle over (1)}to {circle over (5)} are executed in the order as described above. Thetwo-step molding method, however, is different using plural pairs ofplugs and plural female molds in combination, executing the steps{circle over (1)} and {circle over (2)} by using one pair of plugs andone female mold, and executing the steps {circle over (3)}, {circle over(4)} and {circle over (5)} by using another pair of plugs and anotherfemale mold. In other respects, these methods are in common.

In molding the container, the thermoplastic resin sheet must have beenheated at a temperature at which the stretch-molding can be effected.The sheet temperature (Ts) differs depending upon the kind of the resinbut is, usually, not lower than a glass transition temperature (Tg) ofthe resin but is not higher than the crystallization temperature of theresin. In the case of the sheet provided with an amorphous thermoplasticpolyester layer, it is desired that the sheet temperature (Ts) satisfiesthe following formula (7),Tg<Ts<Tg+50° C.   (7)

-   -   (particularly, Tg+20° C.<Ts<Tg+30° C.)    -   wherein Tg is a glass transition point of the thermoplastic        polyester.

When the temperature is not higher than Tg, the stretching becomeslocally excessive in executing the primary molding, and favorablethickness profile is not obtained. When the temperature is not lowerthan Tg+50° C., on the other hand, the sheet is not oriented to asufficient degree, and the container lacks the strength and is whitened,too.

In the present invention, the plug is for stretch-molding the resinsheet and, hence, must have a surface area over at least a predeterminedrange. It is usually desired that the plug has a surface area which isnot smaller than 3 times and, particularly, from 5 to 10 times as greatas the to-be-molded area of the thermoplastic resin sheet.

The to-be-molded area of the thermoplastic resin sheet stands for thearea of the sheet on the inside of a portion that is held as a flange inmolding the sheet.

When the surface area of the plug is smaller than the above-mentionedrange, it becomes difficult to impart molecular orientation to themolded container to a sufficient degree. Namely, the container exhibitsinsufficient mechanical strength, decreased heat resistance and,besides, the walls thereof are whitened during the heat-setting.

The surface temperature Tp of the plug differs depending upon the plugof the first step and the plug of the second step in the one-step methodand the two-step method.

The thermoplastic resin sheet used in the present invention includes apreformed sheet on which the flange portion and the main heat-moldingportion have been shaped in advance. The preformed sheet can be formedby the injection molding, by the compression molding or by press-moldinga flat plate-like sheet.

(One-Step Molding Method)Tg<Tp<Th   (8)

-   -   wherein Tg is a glass transition point of the thermoplastic        polyester, and Th is a heat-setting temperature by using the        female mold described later.

When the plug temperature is lower than the above range, the stretchingbecomes locally excessive in executing the primary molding, and it isnot allowed to obtain the primary molded article having a good thicknessprofile.

When the plug temperature exceeds the above range, on the other hand,the plug exhibits a decreased effect for cooling and imparting theshape.

(First Step in the Two-Step Molding Method).Tg<Tp<Tc tm (9)

-   -   wherein Tg is a glass transition point of the thermoplastic        polyester, and Tc is a crystallization start temperature of the        thermoplastic polyester.

When the plug temperature is lower than the above range, the stretchingbecomes locally excessive in executing the primary molding, and it isnot allowed to obtain the primary molded article having a good thicknessprofile.

When the plug temperature exceeds the above range, on the other hand,the sheet is partly whitened in the initial stage of the stretch-moldingand it is not allowed to obtain the primary molded article having atransparent and favorable surface.

(Second Step in the Two-Step Molding Method).Tg<Tp   (10)

-   -   wherein Tg is a glass transition point of the thermoplastic        polyester, and Th is a heat-setting temperature by using the        female mold described later.

When the plug temperature is lower than the above range, the female moldexhibits a decreased effect for heat-setting, and an extended period ofmolding time is required for accomplishing a predetermined heat-setting.

When the plug temperature exceeds the above range, on the other hand,the plug exhibits a decreased effect for cooling and imparting theshape.

The female mold has a cavity of a size larger than the plug in eitherthe radial direction or the axial direction. Due to the difference inthe size (clearance), the secondary molded article is biaxially orientedas it is being molded with the compressed air. The clearance gives animportant meaning in the lower part of the barrel portion of thecontainer, in preventing the bottom portion from being whitened, in therate of molding and in imparting resistance against deformation byheating.

It is desired that the clearance CL between the plug and the female moldis 0.3 mm≦CL≦1.0 mm and, particularly, 0.5 mm≦CL≦0.75 mm. The CL whichis not larger than 0.3 mm lowers the cooling efficiency, rate ofmolding, heating efficiency and resistance against deformation byheating. On the other hand, the CL which is not smaller than 1.0 mmdeteriorates the shape-imparting performance.

The heat-setting temperature (Th) by the female mold is higher than theresin sheet temperature (Ts) as a matter of course and is, generally,from 120 to 220° C. and, particularly, from 150 to 200° C. When theheat-setting temperature is lower than the above range, the heatresistance is not imparted to a sufficient degree. When the heat-settingtemperature exceeds the above range, on the other hand, the resin of theflange portion is thermally deteriorated resulting in a drop in themechanical strength of the resin.

The heat-resistant resin container of the second embodiment of thepresent invention is obtained by molding the thermoplastic polyestersheet, at least the side wall of the container being oriented andcrystallized by stretching, and the crystallinity in the outer surfaceof the side wall being greater than the crystallinity in the innersurface thereof.

The heat-resistant resin container of the present invention has afeature in that the crystallinity (Co) in the outer surface of the sidewall of the container is greater than the crystallinity (Ci) in theinner surface thereof due to that the outer surface of the secondarymolded article is heat-set upon coming in contact with the inner surfaceof the female mold.

The container of the present invention, therefore, includes the outersurface layer having excellent heat resistance and rigidity, and theinner surface layer having flexibility and impact resistance, which arebeing distributed in the direction of thickness, creating a structurehaving excellent heat resistance and impact resistance in combination.In the flange portion, further, the surface to be heat-sealed has a lowcrystallinity offering an advantage of excellent heat-sealability.

It is desired that the crystallinity (Co) in the outer surface is notsmaller than 20% and, particularly, from 25 to 50%, and that thedifference (Co−Ci) between the crystallinity (Co) in the outer surfaceand the crystallinity (Ci) in the inner surface is not smaller than 10%in the flange portion, and is not smaller than 1% in other portions,from the standpoint of attaining the above-mentioned effect.

The heat-resistant resin container of the present invention has theflange portion, the side wall portion and the bottom portion. Here, itis desired that the ratio (H/D) of the height (H) of the container tothe diameter (D) of the container is not smaller than 0.5 and,particularly, in a range of from 1.2 to 2.3, from the standpoint ofmoldability, imparting molecular orientation and appearance.

In the present invention, the female mold that is used is heated at theheat-setting temperature, and the wall of the flange portion is lesssubject to be molecularly oriented. In general, therefore, the containeris obtained having a flange portion that is cloudy. On the other hand,the side wall of the container is effectively and molecularly orientedsuppressing lamella crystallization and is, hence, transparent whenthere is contained no pigment exhibiting excellent appearance.

The container of the present invention has excellent heat resistancesuppressing a change in the volume to be not larger than 1.0% even afterthe container is heat-treated in an oven at such a temperature that theside wall of the container is heated at 90° C. for 3 minutes.

The molding operation according to the second embodiment of the presentinvention will now be described with reference to FIGS. 8 to 18 of theaccompanying drawings.

(Constitution of the Device)

The device used for the production method of the invention roughlycomprises, as shown in FIG. 8, a plug 1, a female mold 2 and a clampingmetal mold 3.

The plug 1 works to stretch-mold the resin sheet 4 into an article(primary molded article) that comes in agreement with the outer surfaceof the plug, and to shrink-mold it to a final article (tertiary moldedarticle). Here, the primary molded article and the tertiary moldedarticle are nearly in agreement in shape and in size.

If described in further detail, the plug 1 includes a short cylindricalportion 11 that serves as a stack portion of the container in an upperpart on the outer surface thereof, and a tapered portion 12 connected tothe lower side of the cylindrical portion and having a diametercontracting downward. An annular rim 13 is formed along the periphery inthe bottom of the plug 1, the annular rim 13 protruding downward in anarcuate shape by a small distance in cross section. A bottom panel 14 ispositioned in the annular rim 13 and is protruding upward by a smalldistance from the lower end of the rim. A gas passage 15 is formed inthe axial direction of the plug 1 for introducing the compressed air andfor reducing the pressure.

The female mold 2 used in the present invention works to mold theprimary molded article formed by using the plug 1 into a secondarymolded article of a size larger than the primary molded article by usingthe compressed air, and to heat-set the secondary molded article that isformed.

If described in further detail, the female mold 2 has in the upper partthereof a holding surface 25 for holding the peripheral edge of theresin sheet in cooperation with the clamping metal mold 3. Further, agas passage 26 is formed in the central portion of the female mold fordischarging or supplying the gas.

The clamping metal mold 3 is to clamp the peripheral edge of the resinsheet in cooperation with the holding surface of the female mold 2, andcomprises a short hollow cylinder. That is, the clamping metal mold 3has an inner surface 31 of a diameter nearly the same as the cylindricalinner surface of the female mold, and has a holding surface 32 at thelower end thereof for holding the peripheral edge of the disk-like resinsheet.

The plug 1, the female mold 2 and the clamping metal mold 3 are arrangedin concentric, the plug 1 and the female mold 2 being allowed to moverelative to each other in the axial direction (up and down in thedrawing) so as to be in mesh with each other and to separate away fromeach other, and the clamping metal mold 3 being similarly allowed tomove in the axial direction.

(Step of Supplying the Thermoplastic Resin Sheet)

In FIG. 8, either the plug 1 or the female mold 2 is at an ascendedposition and the other one is at a descended position, and the resinsheet 4 heated at a stretching temperature is supplied into between thefemale mold 2 and the clamping metal mold 3.

(Step of clamping/Pre-Stretching the Thermoplastic Resin Sheet)

Then, the clamping metal mold 3 is lowered to hold the peripheral edgeof the resin sheet 4 between the holding surface 25 of the female mold 2and the holding surface 32 of the clamping metal mold 3 as shown in FIG.9.

The resin sheet 4 that is clamped is, then, inflation-deformed in adirection opposite to the direction in which the plug 1 is pushed byusing the compressed air, in order to stretch and orient the stackingportion at the upper part of the side wall of the container. In thisembodiment, therefore, the compressed air is supplied through the gaspassage 26 of the female mold 2 to inflation-deform the resin sheet 4upward like a dome. Therefore, a slightly inner portion of the resinsheet that is clamped is effectively and molecularly oriented toestablish a structure which is thermally and mechanically strong.

(Step of Stretch-Molding into the Primary Molded Article)

The plug 1 is pushed into the resin sheet 4 that is clamped. Referringto FIG. 10, the resin sheet is stretched in a shape in line with theouter surface of the plug 1 except a bottom wall portion 44, and ismolded into a primary molded article 40 a. That is, a flange portion 41is formed between the holding surface 25 of the female mold 2 and theholding surface 32 of the clamping metal mold 3, a stacking portion 42is formed on the outer surface side of the cylindrical portion 11 of theplug 1, and a tapered portion 43 is formed on the outer surface side ofthe tapered portion 12 of the plug 1. Further, a bottom portion 44 isformed so as to be supported by an annular rim portion 13 of the plug 1.

In the embodiment shown in FIG. 10, the plug 1 is used for stretchinginto the primary molded article. In this embodiment, too, a stretchingrod can be used for stretching into the primary molded article as willbe described later with reference to FIG. 39. This enables thetemperature of the plug to be varied from near room temperature up to atemperature not higher than the crystallization initiating temperatureof the thermoplastic resin, which is suited for imparting the shapeafter the shrink back.

(Step of Molding into the Secondary Molded Article with the CompressedAir and of Heat-Setting)

The compressed air is supplied into the interior of the primary moldedarticle 40 a in FIG. 10 through the gas passage 15 in the plug 1 and/ora gap between the plug 1 and the inside of the flange portion of thesecondary molded article 40 b. Referring to FIG. 11, the primary moldedarticle is formed into a secondary molded article 40 b comprising a sidewall portion 42 b along the cylindrical inner surface 22 of the femalemold 2 and a bottom wall portion 44 b along the inner bottom surface 23of the female mold 2.

The inner surface of the female mold 2 has been heated at a temperaturefor heat-setting the resin and, besides, the secondary molded article 40b is pressed onto the inner surface of the female mold 2 due to thecompressed air from the interior. As shown in FIG. 11, therefore, thesecondary molded article 40 b is heat-set due to heat H conducted fromthe female mold 2, whereby the resin is crystallized and distortion inthe mold is relaxed.

(Step of Shrinking into the Tertiary Mold, Imparting the Shape andCooling)

As the secondary molded article 40 b is progressively heat-set and asthe compressed air is no longer supplied from the interior, thesecondary molded article 40 b starts shrinking as shown in FIG. 12.

Then, the pressure is reduced through the gas passage 15 of the plug 1and/or through the above-mentioned gap. As required, the compressed airis supplied through the gas passage 26 of the female mold 2, whereby thesecondary molded article 40 b that is heat-set is correctly shapedfollowing the outer surface of the plug 1 as shown in FIG. 12, and iscooled down into a state in which it can be taken out.

The thus obtained finally molded article (tertiary molded article) 40includes a flange portion 41, a cylindrical stacking portion 42continuous to the inner periphery of the flange portion, a taperedportion 43 contracting downward to be continuous to the lower end of thestacking portion, a rim portion (grounding portion) 46 protrudingdownward to be continuous to the lower end of the tapered portion, and apanel-like bottom portion 45 positioned over the rim portion maintaininga small distance.

(Step of Parting the Tertiary Molded Article)

Finally, referring to FIG. 13, the plug 1 and the clamping metal mold 3ascend, and the tertiary molded article 40 is taken out from the femalemold 2. To accomplish good parting, the air can be blown onto the moldedarticle 40 through the gas passages 15 and 26.

(Two-Step Molding Method)

The two-step molding method is carried out by using a first pair ofplugs 1 a, a female mold 2 a, a clamping metal mold 3 a, a second pairof plugs 1 b, a female mold 2 b and a clamping metal mold 3 b. Thesedevices, however, are basically constituted in the same manner as thoseused in the one-step molding method. The temperature of the female mold2 a in the first step is adjusted to be not higher than the glasstransition point Tg of the resin, and the female mold 2 b in the secondstep is heated at the heat-setting temperature.

The step of supplying the thermoplastic resin sheet in FIG. 14 is thesame as that of FIG. 8, the step of clamping and pre-stretching thethermoplastic resin sheet is the same as that of FIG. 9, the step ofstretching the thermoplastic resin sheet is the same as that of FIG. 10,and the step of molding the primary molded article into the secondarymolded article by using the compressed air in FIG. 15 is the same asthat of FIG. 11. Here, however, the temperature on inner surface of thefemale mold 2 a is adjusted to be not higher than the glass transitionpoint Tg, and the primary molded article 40 a is shaped to acquire theshape of the inner surface of the female mold 2 a to obtain thesecondary molded article 40 b. The plug may have the shape the same asthe finally molded article or different therefrom.

In the step of parting the secondary molded article in FIG. 16, thefemale mold 2 a descends, the plug 1 a and the clamping metal mold 3 aascend, and the secondary molded article 40 b that has not been heat-setis taken out from the female mold 2 a.

In the step of inserting the secondary molded article into the metalmold in FIG. 17, the secondary molded article 40 b is held by the plug 1b and the clamping metal mold 3 b, and is inserted in the cavity 21 ofthe female mold 2 b. The flange portion 41 of the secondary moldedarticle 40 b inserted in the cavity 21 of the female mold 2 b is held bythe holding surface 25 of the female mold 2 b and by the holding surface32 of the clamping metal mold 3 b.

In the step of molding the secondary molded article with the compressedair and heat-setting the secondary molded article in FIG. 18, the wallof the secondary molded article 40 b is pressed onto the inner surfaceof the female mold 2 b that has been heated at a heat-settingtemperature by utilizing the compressed air introduced through the gaspassage 15 of the plug 1 b and/or the gap between the plug 1 and theinner side of the flange portion of the secondary molded article 40 b.

The step of heat-setting the secondary molded article is the same as theone shown in FIG. 11, the step of shrinking the secondary molded articleinto the tertiary molded article, imparting the shape to it and coolingit is the same as the one shown in FIG. 12, and the step of parting thetertiary molded article is the same as the one shown in FIG. 13.Therefore, these steps with reference to these drawings are notdescribed here.

According to the present invention, it is made possible to form thecup-like container having excellent stacking peformance owing to theabove-mentioned basic production method.

In the cup-like container with a flange portion having excellentstacking performance obtained by stretch-molding a thermoplastic resinsheet (preformed sheet) and shaped by shrinking back of the presentinvention, an important feature resides in that a bead portion is formedon the barrel of the cup-like container to protrude inward of thecontainer and a stacking portion is formed at a position under the beadportion.

In the cup-like container with a flange molded by the production methodhaving a step of shrinking from the female mold back onto the male moldas described earlier, the inner diameter of the mouth portion (flangeportion) tends to increase since the mouth portion near the flange doesnot shrink back, arousing a problem in that the stacking portion whichis a step formed relying upon a difference in the inner diameter of thebarrel is not capable of maintaining a sufficiently large overlappingamount with respect to the flange portion of the container located onthe lower side in the stacked state.

The problem of the stacking performance is obvious from FIG. 32. Thatis, FIG. 32 is a side sectional view of a portion in a state where thetwo conventional cup-like containers (upper container 101 and lowercontainer 102) having the same shape are stacked. In the containersshown in FIG. 32, the mouth portion 104 near the flange portion 103 hasbeen crystallized by heat and, hence, has not been shrunk back. As aresult, the inner diameter D1 of the mouth portion is smaller than theouter diameter D2 of the stacking portion 105 formed relying upon thedifference of the inner diameter of the barrel but is larger than theinner diameter D3 of the upper barrel (D2>D1>D3). The lower barrel 107located under the stacking portion 105 has an inner diameter smallerthan the inner diameter D3 of the upper barrel 106, and its innerdiameter decreases toward the lower side.

As will be obvious from the stacked state of FIG. 32, the continers aresuch that the stacking portion 105 of the upper container is placed onthe flange portion 103 of the lower container 102, and the overlappingamount d of the upper and lower containers at the stacked position isexpressed by (maximum diameter−minimum diameter)/2 of the portionscontributing to the stacking. In this case, therefore, the overlappingamount d is expressed by d=(outer diameter D2 of the stackingportion−inner diameter D1 of the mouth portion)/2. In the conventionalcup-like container, a maximum overlapping amount that can be assumed isonly the thickness (outer diameter D2 of the stacking portion−innerdiameter D3 of the upper barrel)/2 of the stacking portion, and anegative value is often assumed. As will become obvious from Examples 18and 19 and Comparative Example 13 appearing later, if the stackingamount increases, the stacking portion of the upper container deviatesfrom the flange portion of the lower container and is deeply overlappedthereon due to the weight of the cup-like container itself that isstacked. Therefore, the upper and lower containers cannot be easilyseparated away from each other (Comparative Example 13).

According to the cup-like container of the present invention as will beobvious from FIG. 33, on the other hand, a bead portion 108 (innerdiameter of the bead portion is D4) has been formed in the lower part ofthe mouth portion 104 to protrude inwardly of the container. When thetwo cup-like containers (upper container 101 and lower container 102) ofthe same shape are stacked, therefore, the stacking portion 105 of theupper container 101 is placed on the bead portion 108 of the lowercontainer 102 to establish the stacked state. Here, as described above,the overlapping amount d of the upper and lower containers is d=(outerdiameter D2 of the stacking portion−inner diameter D4 of the bead)/2. Inthe cup-like container of the present invention, a maximum overlappingamount that can be assumed is {(inner diameter D3 of the upperbarrel−inner diameter D4 of the bead)/2+(outer diameter D2 of thestacking portion−inner diameter D3 of the upper barrel)/2}. As comparedto the conventional cup-like container, therefore, the overlappingamount can be increased by {inner diameter D3 of the upper barrel−innerdiameter D4 of the bead)/2}. As will become obvious from Examplesappearing later, therefore, despite of an increase in the stackingamount, the lower container stably holds the upper container. Namely,the upper and lower containers can be easily separated from each otheroffering excellent stacking performance (Examples 18 and 19).

In the cup-like container having excellent stacking performance of thepresent invention, the bead portion forming the stacking portion isformed at the upper part of the barrel and also works as a reinforcingrib contributing to increasing the mechanical strength of the barrel. Asa result, it is allowed to decrease the thickness from the flangeportion up to the stacking portion.

This is also obvious from the results of Examples 18 and 19 andComparative Example 13 appearing later. Namely, the flange portion up tothe stacking portion are pressed and crushed, and the load is measuredat a moment when the amount of deformation becomes 20% of the initialamount. The cup-like container of the present invention is not deformedeven with a load of not smaller than 70 N, whereas the conventionalcup-like container without the bead shown in FIG. 32 is deformed into20% before the load reaches 70 N, from which a markedly improvedmechanical strength such as rigidity can be comprehended.

In the cup-like container of the invention, the bead may be continuouslyformed along the whole circumference of the barrel. Or, the bead may bedivided into a plurality of portions in the circumferential direction soas to be provided in a number of at least two at opposing positions tomaintain stacking performance when stacked.

In the cup-like container of the invention, it is desired that theoverlapping amount between the upper and lower containers in the stackedstate is maintained to be not smaller than 0.5 mm and, particularly, notsmaller than 0.8 mm though it may vary depending upon the thickness ofthe container. For this purpose, therefore, it is desired that the beadis so formed as to possess the inner diameter D4 which lies in a rangeof (D3−D4)/2 ≧0.5 of the inner diameter D3 of the upper barrel.

In the method of producing the cup-like container with a flange portionhaving excellent stacking performance obtained by stretch-molding amolding precursor, i.e., a thermoplastic resin sheet and, particularly,a preform on which the main heat-molding portion and the flange portionhave been shaped and, then, imparting the shape by shrinking back, animportant feature resides in that a bead portion is formed on the plugused for shaping at a position corresponding to the container barrel toprotrude inward of the container and a stacking portion is formed at aposition under the bead portion.

FIG. 34 is a view illustrating a shaping step by shrink back in theconventional method of producing cup-like containers which are stackedby utilizing the flange portion and the stacking portion, and FIG. 35 isa view illustrating a shaping step by shrink back in the method ofproducing cup-like containers of the present invention which are stackedby utilizing the bead portion and the stacking portion.

As will be obvious from FIGS. 34A and 35A, a molded article 101 has aflange portion 103 fixed by an upper flange-forming mold (UFM) 111 a anda lower flange-forming mold (LFM) 111 b, and is heat-set by a femalemold 110. Referring next to FIGS. 34B and 35B, the molded article 101 isshrunk back onto a plug member 112, shaped to assume the shape of theplug member 112 and is cooled. Here, the flange portion 103 and themouth portion 104 have been thickened or crystallized, and are notshrunk back. Barrels 106 and 107 under the mouth portion are shrunk backonto the plug member 112 from the surface of the female mold 110, shapedto assume the shape of the outer surface of the plug member and are,then, cooled. Here, in the present invention, a bead-forming recessedportion 114 is formed in the plug member 112 in addition to forming astacking portion-forming step 113. On the cup-like container that isformed, therefore, there are formed not only the stacking portion 105but also the bead portion 108 protruding inward of the container.

Basic steps of the method of producing the cup-like container havingexcellent stacking performance of the invention will now be described indetail.

(1) Step of Forming the Molding Precursor.

In the present invention, first, there is formed, as a moldingprecursor, a thermoplastic resin sheet and, particularly, a preform onwhich the main heat-molding portion and the flange portion have beenshaped in advance. The molding precursor may be either a sheet or apreform which has been shaped. The preform may have any shape such as ashallow bottom or a deep bottom provided it has a flange portion. Thepreform can be formed by various methods such as injection molding orcompression molding.

In an embodiment illustrated in FIG. 36, a molding precursor 120 isconstituted by a main heat-molding portion 121 of the shape of nearly adisk and an annular flange 122 portion surrounding it. In an embodimentdescribed below, the flange portion 122 of the molding precursor has notbeen crystallized, and is crystallized after having been fed into theheat-molding device but before being heat-molded. However, the flangeportion may have been crystallized by heat by using a heater prior tobeing fed to the heat-molding device or may have been thickened withoutbeing crystallized by heat. As for the thickness of the flange portionof the molding precursor, it is desired that the flange portion has athickness of about 1 to 3 times as large as that of the flange portionof the cup-like container which is the final molded article.

As the thermoplastic resin that can be preferably used as the moldingprecursor 120, though not limited thereto only, there can be used apolyolefin resin, a polystyrene resin, a polyamide resin or apolycarbonate resin in addition to a polyester resin that will bedescribed later.

Further, the molding precursor may have a plurality of layers as will bedescribed later not being limited to the single layer structure only ofthe above resins.

(2) Feeding to the Heat-Molding Device.

If further described with reference to FIG. 37, the molding precursor120 taken out from the compression-molding apparatus or theinjection-molding apparatus (not shown) is heated to a requiredheat-molding temperature and is, then, fed to the heat-molding apparatus123.

When the molding precursor 120 is obtained substantially in an amorphousform such as when it is made of a polyester resin, it is desired thatthe molding precursor 120 is heated at a temperature not lower than theglass transition temperature (Tg) but lower than the crystallizationinitiating temperature (Tic). When the heating temperature is lower thanthe glass transition temperature (Tg), a very large force is requiredfor the heat-molding. When the heating temperature is not lower than thecrystallization initiating temperature (Tic), on the other hand,spherulites tend to be formed to impair the transparency. The glasstransition temperature (Tg) and the crystallization initiatingtemperature (Tic) used in the specification are those found from a DSCcurve obtained by arbitrarily picking up about 10 mg of the moldedarticle to be measured, holding it in a nitrogen gas atmosphere at 300°C. for 3 minutes by using a differential scanning calorimeter (DSC),quickly cooling it down to room temperature and heating it at a rate of20° C. a minute.

The heat-molding apparatus 123 that is shown includes a female moldingmember 130, a pressing/fastening member (upper flange mold) 132, a plugmember 134 and an extending rod 136. The female molding member 130 has amolding cavity 138 formed extending downward from the upper surfacethereof. The molding cavity 138 has a cylindrical shape in the upperpart of the inner peripheral surface thereof and is forming a step 115corresponding to the stacking portion. The intermediate portion and thelower portion of the inner peripheral surface thereof are of the shapeof an inverted circular truncated cone of which the inner diametergradually decreases downward, and the bottom surface is a substantiallyhorizontal circular shape.

The female molding member 130 further has a communication hole 140penetrating through the bottom wall thereof. The pressing/fasteningmember 132 is of an annular shape, and an opening arranged at the centerthereof has an inner diameter substantially the same as the innerdiameter at the end of the molding cavity 138 formed in the femalemolding member 130.

The plug member 134 has an upper portion of a cylindrical shape and alower portion of the shape of an inverted circular truncated cone ofwhich the outer diameter gradually decreases downward. In theillustrated embodiment, a stepped portion 113 for forming the stackingportion and a recessed portion 114 for forming the bead are formed alongthe whole circumferential direction on the outer surface of the plugmember 134.

The plug member 134 has a through hole 142 penetrating and extendingtherethrough in the axial direction thereof. The extending rod 136 is ofa slender cylindrical shape and is inserted in the through hole 142 inthe plug member 134. The through hole defined in the extending rod 136of the cylindrical shape works as a communication hole 144.

Referring to FIG. 37, the molding precursor 120 heated at a requiredheat-molding temperature is placed on the upper surface of the femalemolding member 130, and its main heat-molding portion 121 is positionedso as to be corresponded to the molding cavity 138.

(3) Step of Crystallizing the Flange Portion.

Referring to FIG. 38, the molding precursor 120 is placed on the uppersurface of the female molding member 130 in a manner that the mainheat-molding portion is opposed to the molding cavity 138, and thepressing/fastening member 132 is lowered, whereby the flange portion 122of the molding precursor 120 is pressed and fastned between the uppersurface of the female molding member 130 and the lower surface of thepressing/fastening member 132.

When the flange portion is to be crystallized to impart heat resistanceto the flange portion 122 prior to the heat-molding, the flange portion122 is crystalled by being locally heated at the crystallizationinitiating temperature (Tic) up to lower than the meting point (Tm)thereof. According to the present inventor's experience, further, whenthe flange portion 122 heated at not lower than the glass transitiontemperature is pressed by a considerable pressure, such as about 4.5 toabout 13 MPa, the flange portion 122 stretches, the thickness of theflange portion 122 decreases to, for example, about one-third to aboutone-half, and the flange portion is crystallized by orientation due tothe fluidity of the resin. Further, by bringing the flange portion 122into contact with the upper surface of the female molding member 130heated at the crystallization initiating temperature (Tic) up to lowerthan the melting point (Tm) thereof, it is made possible to relax themolding strain caused by the flow and orientation of the resin and toeffect the crystallization to impart heat resistance. The heatresistance and strength of the flange portion 122 are improved by thecrystalliztion and by the relaxation of the molding strain.

In the illustrated embodiment, the pressing/fastening member 132 islowered to press and fasten the flange portion 122; i.e., the flangeportion 122 is crystallized. By lowering the pressssing/fastening member132, therefore, the flange portion 122 is fastened and is crystallized.

In the illustrated embodiment, the preform is used as a moldingprecursor. Even when a sheet is used, a portion that becomes a flangeportion is crystallized upon executing the step of fastening, and acup-like container is molded like when the preform is used.

The step of crystallizing the flange portion is carried out by using thefemale molding member 130 of a predetermined temperature, and fasteningthe flange portion 122 of the molding precursor 120 placed on the upperend of the female molding member 130 by using the pressing/fasteningmember 132. However, the step of crystallizing the flange portion canalso be carried out by using a separate support member without using thefemale molding member 130. In this case, the flange portion 122 of themolding precursor 120 supported on the support member heated at apredetermined temperature, may be fastened by the pressing/fasteningmember 132 to execute the step of crystallizing the flange portion.Thereafter, the molding precursor may be introduced onto the femalemolding member 130.

(4) Step of Heat-Molding.

The main heat-molding portion 121 of the molding precursor 120 isheat-molded following the step of crystallizing the flange portion 122on the female molding member 130. In the illustrated embodiment, theheat-molding is effected in three stages, i.e., extension by using thestretching rod 136, blow-molding and shrink back.

In the first stage in the step of heat-molding, the stretching rod 136is lowered down to a position shown in FIG. 39, whereby the mainheat-molding portion 121 of the molding precursor 120 is stretched inthe axial direction.

Next, in the second stage as shown in FIG. 40, the communication hole144 of the stretching rod 136 is communicated with a source ofcompressed air (not shown), the main heat-molding portion 121 that isstretched is blow-molded by the action of the compressed air blown fromthe communication hole 144 to assume the molding shape of the femalemolding member 130, i.e., to assume the shape corresponding to the innersurface of the molding cavity 138. In conducting the blow-molding, thefemale molding member 130 is heated by suitable heating means (notshown) such as an electric resistance heater, so that the inner surfaceof the molding cavity 138 assumes a temperature of not lower than thecrystallization initiating temperature of the thermoplastic resin butlower than the melting point thereof. The main heat-molding portion 121that is blow-molded is heated upon coming in contact with the innersurface of the molding cavity 138 of the female molding member 130, andis heat-set.

The heat-setting temperature is higher than the crystallizationinitiating temperature (Tic) of the thermoplastic resin but is desirablylower than the melting point (Tm) thereof and, particularly, not higherthan the melting point (Tm) thereof minus 10° C. When the heat-settingtemperature is not lower than the melting point (Tm), the mainheat-molding portion 121 tends to be melt-adhered onto the femalemolding member 130. When the heat-setting temperature is lower than thecrystallization initiating temperature (Tic), on the other hand, thecrystallization is not enough, the molding strain is not relaxed to asufficient degree, and the heat resistance and the strength are notobtained.

In the third stage of the step of heat-molding, the plug member 134 islowered down to a position shown in FIG. 41, the communication hole 144of the stretching rod 136 is communicated with a vacuum source (notshown), and the communication hole 140 of the female molding member 130is communicated with the source of compressed air (not shown). Due tothe suction of evacuation and the compressed air pressure, therefore,the main heat-molding portion 121 shrinks back, and the molding shape ofthe plug member 134 assumes the final shape, i.e., assumes the shape ofthe outer surface of the plug member 134 having the step portion 113 forforming the stacking portion and the recessed portion 114 for formingthe bead portion, and the final shape and is imparted to the container146. Further, the main heat-molding portion 121 is cooled upon coming incontact with the plug member 134. Here, the temperature on the surfaceof the plug member 134 may lie within a suitable range of from near roomtemperature up to not higher than the crystallization initiatingtemperature.

The container 146 is taken out from the heat-molding apparatus 123 afterit has been cooled to a sufficient degree. Referring to FIG. 42, thecontainer 146 that is taken out includes an annular flange 148, a sidewall 150 hanging down from the inner peripheral edge of the flange 148,and a bottom wall 152 closing the lower end of the side wall 150. Thestacking portion 105 and the bead portion 108 are formed on the sidewall 150.

In the illustrated embodiment as represented by a two-dot chain line inFIG. 42, further, the press-stretched flange 148 is trimmed to obtain acontainer having a desired outer diameter. The flange 148 can be trimmedin a customary manner.

The method of producing the cup-like container having excellent stackingperformance of the invention is in no way limited to the methodconcretely illustrated in FIGS. 37 to 42 above, but may be anyconventional method of heat-setting the molded article that has beenstretched, and imparting the shape to the article by shrinking it backonto the male mold (plug member) and cooling it, so far as the stackingportion and the bead portion can be formed at the time of imparting theshape.

In the above embodiment, for example, the molding precursor is put tothe blow-molding after it has been stretched by using the stretchingrod. The molding precursor, however, may be blow-molded without usingthe stretching rod. Further, the molding precursor may be stretched byfree-blow-molding without using the female mold. In this case, theheat-setting can be effected by using a heating oven or the like.Moreover, the molding precursor may be directly stretched by using themale mold (plug member). In this case, after stretched with the plugmember, the compressed air is fed to between the plug and thestretch-molded article, whereby the article comes in contact with thesurface of the female mold heated at the heat-setting temperature, andis heat-set.

In the above embodiment, the molding precursor is shaped and cooled uponcoming in contact with the plug member. The molding precursor can alsobe cooled by cold-blow as a matter of course.

When a sheet that has not been shaped is used as the molding precursor,it is desired that the sheet is clamped by a jig (female molding member130 and pressing/fastening member 132 in the Embodiment shown in FIG.38) and a portion that becomes a flange is crystallized by orientationbased on the fluidization of the resin and by heating like in the caseof the above-mentioned preform shown in FIG. 38. Even when the sheet isused, therefore, the flange portion, too, of the cup-like container thatis formed exhibits excellent heat resistance and impact resistance.

In crystallizing the flange portion of the molding precursor, it is alsoallowable to selectively crystallize the lower side of the flangeportion to produce a cup-like container with a flange having excellentheat-sealing performance.

That is, the lower surface of the flange portion is selectivelycrystallized, and the upper surface of the flange portion is left toremain amorphous or lowly crystalline. Namely, the heat resistance ismaintained by the crystallization of the lower surface of the flange,while the upper surface which is the heat-sealing surface remainsamorphous or lowly crystalline and is softened or becomes viscous makingit possible to easily heat-seal the sealing member such as an aluminumfoil.

If roughly divided, the flange portion can be selectively crystallizedby two means of selective crystallization by orientation and selectivecrystallization by heating.

FIG. 43 is a view illustrating the selective crystallization byorientation, wherein a protrusion 160 that serves as a heat-sealingportion is formed on the upper surface 122 a of the flange portion 122of the molding precursor 120. The flange portion 122 forming theprotrusion 160 is press-stretched by being sandwiched between a pair ofannular flange-forming molds, i.e., between the upper flange-formingmold (UFM) 111 a and the lower flange-forming mold (LFM) 111 b. Arecessed portion 162 is formed in the UFM 111 a so as to be correspondedto the protrusion.

That is, the protrusion 160 formed on the upper surface 122 a issuppressed from being fluidizing owing the recessed portion 162 in theUFM 111 a even when the press-stretching is effected by using the aboveUFM 111 a and LFM 111 b under a pressure (about 4.5 to about 13 MPa)which causes the crystallization by orientation being heated at atemperature higher than the glass transition temperature. As a result,the flange portion 122 is crystallized by orientation due to thefluidization of the resin, but the protrusion 160 formed on the uppersurface 122 a is not crystallized by orientation since the resin issuppressed from fluidized in the direction of the flange surface, andthe amorphous or lowly crystalline state is maintained.

The selective crystallization by heating is to crystallize by heat theflange portion 122 in a manner that the upper surface 122 a side of theflange portion 122 is not crystallized by heat while preventing theflange portion 122 of the molding precursor 120 from beingpress-stretched. The selective heating includes the one of the contacttype and the one of the radiant heat type.

FIG. 44 illustrates the method of selective heating of the radiant heattype. According to this method, the selective heating is effected in astate where the flange portion 122 of the molding precursor 120 isbrought into contact with an annular metal mold 170 for cooling and isheld by a holding metal mold 172. That is, a cooling water passage 170 ais formed in the annular metal mold 170 which is in contact with theprotrusion 122 a of the flange portion 122, and cooling water is flownthrough the cooling water passage 170 a to cool the protrusion 122 a ofthe flange portion 122. On the outer side of the flange portion, aheater 173 (e.g., infrared ray heater) is arranged maintaining asuitable distance to heat the lower surface 122 b of the flange portion122 by the radiant heat thereby to effect the selective heating.

According to the method of selective heating of the contact type, theselective heating is effected in a state where an annular metal mold forcooling which is the same as the one used in the radiant heat type isbrought into contact with the protrusion of the flange portion, and theflange portion is held by the annular metal mold for heating. The lowersurface of the flange portion is heated by heat conducted from a bandheater attached to the outer surface of the annular metal mold forheating.

In selectively crystallizing the flange portion 122 described above, theselective crystallization by orientation shown, for example, in FIG. 43is effected prior to the step of heat-molding the molding precursor 120,and the selective crystallization by heating shown in FIG. 44 iseffected prior to the step of heat-molding the molding precursor 120 orsimultaneously with the heat-set based on the oven-heating in the stepof heat-molding.

Third Embodiment

In this embodiment of the invention, the heat-resistant container isproduced in three steps; i.e., forming a pre-molded article, forming anintermediate article and forming a final container. Here, adistinguished feature resides in that the intermediate article is formedand the final container is formed both by heating (heat-setting) thesolid-phase-molded article, heat-shrinking the molded article, andcooling and shaping the heat-shrunk article.

That is, by conducting the solid-phase molding in one step, the wall ofthe final container is molecularly oriented (surface oriented) to aconspicuous degree not only in the barrel portion but also in the centerof the bottom portion. Upon conducting the heat-setting in the secondstep following the solid-phase molding, further, the orientation andcrystallization are promoted. Moreover, by effecting the heat-shrinkingfollowing the heat-setting, the distortion is effectively relaxed.

In the heat-resistant container of the present invention, therefore,deformation due to heat is effectively prevented at the time ofheat-sterilization such as sterilization by boiling even in the bottomportion which is an important portion for imparting the self-standingperformance to the container or for imparting self-standing stability.Besides, the barrel portion of the container exhibits excellent impactresistance withstanding the impacts of when it falls down. Even in thebottom portion which can be least oriented, no spherulite is formed,exhibiting not only excellent impact resistance but also very goodappearance such as transparency.

Upon effecting the heat-shrinking between the heat-setting and thecooling/shaping, further, good heat efficiency is accomplished since thefunctions are separated between the heating portion and the coolingportion as compared to when the heating and cooling are effected in thesame portion and, besides, the time for occupying the mold can beshortened. Therefore, the method of the present invention accomplishessuch advantages as decreasing the energy cost and improving theproductivity.

(1) Molding into the Pre-Molded Article.

In the present invention, the pre-molded article is desirably obtainedby molding the sheet in solid phase, i.e., by pressing the sheet usingthe plug for pre-molding, the sheet being clamped by the clamping metalmold and by the female mold for pre-molding, and by supplying thecompressed gas into between the sheet and the plug.

In molding the sheet in this case, it is desired that the sheet ismaintained at a temperature of from the glass transition point (Tg) ofthe thermoplastic polyester +15° C. to the glass transition point +40°C. The range of from the glass transition point +15° C. to the glasstransition point +40° C. is the one where the PET resin is mostefficiently oriented and crystallized. When the sheet temperature islower than the above range, the resin is over-stretched at the time ofmolding and is whitened. When the sheet temperature is higher than theabove range, on the other hand, the resin is not oriented orcrystallized to a sufficient degree and tends to become whitened in asubsequent step of heat-setting due to heat crystallization.

In forming the pre-molded article, further, it is desired to maintainthe plug at a temperature of from the glass transition point of thethermoplastic polyester −30° C. to the glass transition point +20° C.When the plug temperature lies outside this temperature range, the resintemperature at the contact portion undergoes a change due to the contactwith the plug during the stretch-molding, and the stretching is notevenly effected.

It is further desired to maintain the female mold for pre-molding at atemperature of from the glass transition point of the thermoplasticpolyester +10° C. to the glass transition point +50° C. In order toefficiently promote the orientation and crystallization in the bottomportion of the pre-molded article, the female metal mold must bemaintained at a temperature of from the glass transition point +10° C.of the thermoplastic polyester to the glass transition point +50° C.

The plug used for stretch-molding the resin sheet into the pre-moldedarticle must have a surface area which lies at least within apredetermined range. It is, generally, desired that the plug has asurface area which is not smaller than 3 times and, particularly, from 5to 10 times as large as the area to be molded of the thermoplastic resinsheet.

The area to be molded of the thermoplastic resin sheet stands for thearea of the sheet on the inside of a portion that is held as a flange inmolding the sheet.

When the surface area of the plug is smaller than the above range, itbecomes difficult to molecularly orient the molded container to asufficient degree; i.e., the container exhibits insufficient mechanicalstrength, decreased heat resistance, and is whitened on the walls duringthe heat-setting.

(2) Molding into an Intermediate Article.

It is desired that an intermediate article is molded from the pre-moldedarticle by inserting the pre-molded article in the female mold forintermediate molding of which the temperature is adjusted whilesupporting the pre-molded article by the plug for intermediate molding,by shrinking the molded article along the outer surface of the plug, andshaping and cooling the molded article.

It is desired that the female mold for intermediate forming ismaintained at a temperature of not lower than the crystallization starttemperature of the thermoplastic polyester. The molded articleefficiently heat-shrinks when the temperature of the female mold ishigh. When the temperature is set to be lower than this range, however,the molded article cannot be shrunk along the outer surface of the plug.

It is desired that the temperature of the plug for intermediate moldingis not higher than the temperature of the female mold for intermediatemolding and is maintained in a range of from 80 to 110° C. Thetemperature of the plug must be set in a region lower than thetemperature of the female mold. When the temperature is lower than theabove range, the molded article is not efficiently heated by theconduction of heat, and the time for heat-shrinking becomes long. Whenthe temperature is higher than this range, on the other hand, the moldedarticle is not cooled to a sufficient degree and undergoes deformationdue to shrinkage after the step of parting.

In the present invention, it is desired that the surface area of thepre-molded article is from 1.1 times to 1.5 times as large as thesurface area of the intermediate product from the standpoint of removingdistortion and moldability. That is, when the surface area is smallerthan the above range, the distortion is not removed to a sufficientdegree due to heat shrinking. When the area is larger than the aboverange, on the other hand, wrinkles develop on the surface of theintermediate product due to the lack of shrinking, and the intermediatearticle is not favorably shaped.

(3) Molding into a Final Container.

In the method of the present invention, it is desired that the femalemold for final molding is maintained at a temperature of not lower thanthe crystallization start temperature of the thermoplastic polyester.The female mold must be maintained at a temperature not lower than thecrystallization start temperature from the standpoint of promoting thecrystallization. Due to the heat-setting at this temperature, theorientation and crystallization proceed to a sufficient degree, and thefinal container exhibits improved heat resistance.

It is further desired that the plug for the final container ismaintained at a temperature in a range of from the glass transitionpoint of the thermoplastic polyester −20° C. to the glass transitionpoint +20° C. When the temperature is lower than this range, the step ofheat-setting is not efficiently effected by the conduction of heat. Whenthe temperature is higher than this range, the cooling is not effectedto a sufficient degree, and the molded article undergoes deformation dueto shrinkage after the step of parting.

In the present invention, it is desired that the surface area of thefemale mold for final molding is from 1.01 times to 1.10 times as largeas the surface area of the plug for the final container from thestandpoint of removing distortion and moldability. That is, when theratio of the surface areas is smaller than the above range, thedistortion is not removed to a sufficient degree due to heat shrinking.When the ratio of the surface areas is larger than the above range, onthe other hand, wrinkles develop on the surface of the final container,and the final container is not favorably shaped.

The molding operation according to a third embodiment of the presentinvention will now be described with reference to FIGS. 20 to 30 of theaccompanying drawings.

(Constitution of the Devices)

The devices used in the production method of the present invention arethe same as shown in FIGS. 8 to 19. The device used in the one-stepmolding roughly includes a plug 11, a female mold 12 and a clampingmetal mold 13 as shown in FIG. 20.

Further, the device used in the two-step molding includes a plug 21, afemale mold 22 and a clamping metal mold 23 as shown in FIG. 23.

Further, the device used in the three-step molding includes a plug 31, afemale mold 32 and a clamping metal mold 33 as shown in FIG. 27.

The plug 11 for the one-step molding assists the stretch-molding of thepolyester sheet 4 into the pre-molded article 5, the plug 21 for thetwo-step molding has an outer shape for shrinking and shaping thepre-molded article 6 into an intermediate particle 6, and the plug 31for the three-step molding has an outer shape for shrinking and shapingthe intermediate article 6 into a finally molded article 7.

More specifically, the plug 11, plug 21 and plug 31, in common, have ashort cylindrical portion 14 that serves as a stacking portion of thecontainer at an upper part of the outer surface, and a tapered portion15 connected to the lower side of the cylindrical portion and having adiameter that is contracting downward. An annular rim 16 is formed alongthe periphery on the bottom of the plugs 11, 21, 31, protruding downwardin a nearly arcuate shape by a small distance in cross section. A bottompanel portion 17 is positioned inside the annular rim 16 protrudingupward by a small distance from the lower end of the rim. A gas passage18 is formed in the axial direction of the plugs 11, 21, 31 forintroducing the compressed air and for reducing the pressure.

The female mold 12 for the one-step molding used in the presentinvention is for defining the shape of the pre-molded article 5 moldedby using the compressed air, the female mold 22 for the two-step moldingis for heating the pre-molded article 5 and for shrinking it into theintermediate article 6, and the female mold 32 for the three-stepmolding is for heat-setting the intermediate article 6 by heating it andfor shrinking it into the final molded article 7.

If described in further detail, the female mold 12, female mold 22 andfemale mold 32, in common, have, at their upper parts thereof, a holdingsurface 25 for holding the peripheral edge of the resin sheet, of thepre-molded article or of the intermediate article in corporation withpairs of clamping molds 13, clamping molds 23 and clamping molds 33.Further, a gas passage 26 is formed in the central portions of thefemale molds for discharging and supplying the gas.

The clamping metal molds 13, 23 and 33 work to clamp the peripheral edgeof the resin sheet, of the pre-molded article or of the intermediatearticle in cooperation with the holding surfaces of the female molds,and comprise short hollow cylinders. That is, the clamp metal molds 13,23 and 33 have an inner surface 34 of a diameter nearly the same as thatof the cylindrical inner surface of the female mold, and have, at thelower ends thereof, a holding surface 35 for holding the peripheral edgeof the disk-like resin sheet.

The plug 11 (21, 31), female mold 12 (22, 32) and the clamping metalmold 13 (23, 33) are arranged in concentric, the plug 11 (21, 31) andthe female mold 12 (22, 32) being provided to move relative to eachother in the axial direction (up and down in the drawing) so as to comein mesh with each other and to separate away from each other, and theclamping metal mold 13 (23, 33) being similarly provided to move in theaxial direction.

(First Molding Step)

Step of Clamping the Sheet.

In FIG. 20, either the plug 11 or the female mold 12 is at the ascendedposition and the other one is at the descended position, and the resinsheet 4 heated at a stretching temperature is supplied to between thefemale mold 12 and the clamping metal mold 13.

The polyethylene terephthalate sheet 4 heated at a molding temperatureof 105° C. is clamped by the clamping metal mold 13 and by the femalemold 12, and is molded.

The polyethylene terephthalate used in this embodiment has an inherentviscosity (IV) of 0.8, a glass transition point (Tg) of 70° C. and asheet thickness of 1.2 mm.

Step of Stretching/Shaping.

Referring to FIG. 21, the sheet 4 is stretched, oriented andcrystallized as the plug 11 of which the temperature is adjusteddescends. Immediately thereafter, the compressed air (0.6 MPa) isintroduced through the gas passage 18 in the plug and through a gapbetween the plug and the molded article and, as required, vacuum isintroduced through the gas passage 26 of the female mold, whereby themolded article is pressed onto the female mold 12 adjusted at 100° C.and is shaped to be in conformity with the shape of the inner walls ofthe female mold.

Pre-molded Article.

The plug 11 is ascended, and the clamping metal mold 13 and the femalemold 12 are opened to take out the pre-molded article 5 that has beenoriented and crystallized.

Referring to FIG. 22, the pre-molded article 5 includes a cylindricalbarrel portion 51, a closed bottom portion 52 continuous to the lowerend of the barrel portion and a flange portion 53 continuous to theupper end of the barrel portion.

(Second Molding Step)

An intermediate article 6 is formed from the pre-molded article 5 formedin the first molding step.

Step of Insertion in the Metal Mold.

In FIG. 23, the pre-molded article 5 is supported by the plug 21 and isinserted in the female mold 22.

Step of Heat-Shrinking.

In FIG. 24, the pre-molded article 5 heat-shrinks due to the conductionof heat from the inner wall of the female mold 22 heatd at 180° C.

Step of Cooling/Shaping.

Referring to FIG. 25, the pre-molded article 5, then, shrinks up to theouter surface of the plug 21 and, nearly at the same time, cooled andshaped by the outer surface of the plug 21 heated at 110° C. due tovacuum through the gas passage 18 of the plug and through the gapbetween the plug and the molded article and, further as required, due tothe compressed air through the gas passage 26 of the female mold 22.

Intermediate Article.

The clamping metal mold 23 and the female mold 22 are opened and theplug 21 is ascended to take out the intermediate product 6 that isshrunk. Here, as required, the air is blown from the outer side to coolthe intermediate article so that it is quickly parted.

As shown in FIG. 26, the intermediate product 6 that is formed includesa short cylindrical stacking portion 61 and a tapered portion 62 havinga diameter contracting downward. The lower end of the tapered portion isclosed by a bottom panel portion 64 through an annular rim 63 thatprotrudes downward. Further, a flange portion 65 is formed at the upperend of the stacking portion 61.

(Third Molding Step)

A finally molded article 7 is formed from the intermediate article 6formed in the second molding step. Step of insertion in the metal mold.

In FIG. 27, the intermediate article 6 is supported by the plug 31 andis inserted in the female mold 32.

Step of Heat-Setting.

In FIG. 28, the compressed air (0.6 MPa) is introduced through the airvent 18 of the plug and through the gap between the plug and the moldedarticle and, as required, vacuum is introduced through the vent 26 ofthe female mold in order to heat-set the molded article 6 a whilepressing it onto the surface of the female mold 32 heated at 200° C.

Step of Shrinking/Shaping.

Referring next to FIG. 29, the molded article starts heat-shrinking dueto the transfer of heat from the female mold 32. Further, vacuum isintroduced through the gas passage 18 of the plug 31 and through the gapbetween the plug and the molded article and further, as required, thecompressed air is introduced through the gas passage 26 of the femalemold 32, so that the molded article shrinks up to the outer surface ofthe plug 31 and that the molded article is cooled and Shaped into thefinally molded article 7 due to the contact with the plug 31 heated at90° C.

Step of Parting.

Finally, the female mold 32 and the clamping metal mold 33 are opened asshown in FIG. 30, and the plug 31 is ascended to take out the finallymolded article 7.

Fourth Embodiment

A preferred container of the present invention is obtained byheat-molding a sheet having a thermoplastic polyester layer comprisingchiefly an ethylene terephthalate unit, and includes a flange portion, abarrel portion and closed bottom portion, and has a feature in that thethermoplastic polyester in the bottom portion of the container has acrystallinity of not smaller than 15% and the bottom portion of thecontainer is substantially transparent and exhibits a distinguisheddiffraction peak on the surface of an index of a plane (010) in theX-ray diffraction.

Though the container of this type of the invention is obtained byheat-molding the thermoplastic polyester sheet, the thermoplasticpolyester in the bottom portion of the container exhibits acrystallinity of not smaller than 15% and, hence, excellent heatresistance. Besides, the bottom portion of the container exhibitsastonishing properties in combination, i.e., a distinguished diffractionpeak on the surface of an index of a plane (010) in the X-raydiffraction, and substantial transparency.

In obtaining the container by molding the sheet, it is relatively easyto molecularly orient the barrel portion by stretching. It is, however,relatively difficult to molecularly orient the bottom portion bystretching. It is, however, important to impart the required propertiesto the bottom portion of the container even though it is the oneobtained by molding the sheet from the practical point of view. Forexample, the bottom portion of the container that has not beenmolecularly oriented to a sufficient degree is liable to be cracked dueto impacts such as of when it is caused to fall down. Further, thebottom portion of the container having insufficient heat resistance isdeformed during the sterilization by heating depriving the container ofthe self-standing performance and standing stability.

When the sheet-molded container is heat-treated such as heat-set inorder to impart heat resistance thereto, the bottom portion is whitenedto a conspicuous degree arousing such a problem that a purchaser maydoubt the content has been degenerated (e.g., dregs have beenprecipitated).

According to the embodiment of the present invention, the surface isoriented even at the center of the bottom portion of the container so asto exhibit a distinguished diffraction peak on the surface having anindex of a plane (010) by the X-ray diffraction and, besides, the bottomportion is crystallized to possess a crystallinity of not smaller than15%. Thus, there are obtained excellent impact resistance and heatresistance effectively preventing the center of the bottom portion frombeing whitened and maintaining transparency even at the center of thebottom portion.

FIG. 31 shows an X-ray diffraction image at the center of the bottomportion of the container of the present invention measured as describedabove.

From a comparison of the X-ray diffraction image of the bottom portionof the PET container of the invention shown in FIG. 31 with the X-raydiffraction image of the crystalline PET shown in FIG. 4, it is obviousthat the diffraction peak is conspicuously exhibited on the surface ofan index of a plane (010) in the bottom portion of the container of theinvention while the diffraction peak is disappearing from the surface ofan index of a plane (100).

In the bottom portion of the container of the present invention, theX-ray diffraction image is distinctly exhibited as shown in FIG. 31,i.e., the diffraction peak is ditinctly exhibited on the surface of theindex of a plane (010) while the diffraction peak is disappearing fromthe surface of the index of a plane (100), from which it is reasonableto consider that a benzene plane has been arranged in parallel with thewall surface in the bottom portion of the container.

That is, in the X-ray diffraction method, if the benzene plane is nearlyin parallel with the surface of the sample sheet, the diffraction is notmeasured on the plane (100) but the diffraction is measured on the plane(010) nearly at right angles thereto. Thus, a large diffraction peakintensity on the plane (010) means that the benzene plane of a unit ofethylene terephthalate is in parallel with the surface of the sheet.Conversely, a large diffraction peak intensity on the plane (100) meansthat the benzene plane of a unit of ethylene terephthalate is inclinedrelative to the film surface and is not in parallel therewith.

It is thus obvious that the surface has been oriented to a conspicuousdegree on the wall even at the center of the bottom portion of thecontainer of the present invention.

The wall has a crystallinity of not smaller than 15% at the center inthe bottom portion of the container of the present invention.

In the container of the present invention, even the center of the bottomportion has been crystallized. However, the crystals are not those(spherulite) of the type but are the crystals that are oriented offeringsuch advantages as excellent heat resistance and impact resistance aswell as excellent transparency.

The wall at the center of the bottom portion of the container of thepresent invention exhibits a haze value of, generally, not larger than20% and, particularly, not larger than 10% as measured by using ahazeometer manufactured by Suga Shikenki Co.

In the container of the present invention, the wall at the center of thebottom portion has been crystallized due to the surface orientation asdescribed already. The crystallinity due to the orientation can beevaluated in terms of the oriented crystallization tendency (U)represented by the above-mentioned formula (I).

That is, as described already, the diffraction peak intensity on thesurface of an index of a plane (010) by PSPC-MDG is related to thedegree of orientation of the surface of the wall. The orientedcrystallization tendency (U) represented by the above-mentioned formula(I) is to represent the diffraction peak intensity H (010) which isstandardized with the diffraction peak intensity on the surface of anindex of a plane (−110). The larger this value, the larger the degree ofcrystallization due to orientation.

In the present invention, it is desired that the orientedcrystallization tendency (U) is not smaller than 1.3 at the center ofthe bottom portion from the standpoint of impact resistance, heatresistance and transparency.

It is desired that the container of the present invention is obtained bysolid-phase-molding the sheet which contains a thermoplastic polyesterand, more particularly, by solid-phase-molding the sheet through atleast two steps of stretching and a step of heat-shrinking.

More concretely, the container of the invention is preferably producedby the method shown in FIGS. 20 to 30 and described by way of the thirdembodiment.

[Polyester]

The polyester sheet may be the one of a single polyester layer or amulti-layer sheet comprising a polyester layer and other resin layers.

In the present invention, the polyester constituting a sheet of at leastone layer is a polyester of which the thermoplastic polyester is derivedfrom a carboxylic acid component comprising chiefly an aromaticdicarboxylic acid and from an alcohol component comprising chiefly analiphatic diol and, particularly, is a polyester in which not less than50 mol % of the carboxylic acid component comprises a terephthalic acidcomponent and of which not less than 50 mol % of the alcohol componentcomprises an ethylene glycol component.

The polyester may be a homopolyester, a copolymerized polyester, or ablend of two or more kinds thereof provided the above-mentionedconditions are satisfied.

Examples of the carboxylic acid component other than the terephthalicacid component, include isophthalic acid, naphthalenedicarboxylic acid,P-β-oxyethoxybenzoic acid, biphenyl-4,4′-dicarboxylic acid,diphenoxyethane-4,4′-dicarboxylic acid, 5-sodiumsulfoisophthalic acid,hexahydoterephthalic acid, adipic acid, sebacic acid, trimellitic acidand pyromellitic acid.

As the alcohol component other than ethylene glycol, on the other hand,there can be exemplified 1,4-butanediol, propylene glycol, neopentylglycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol,cyclohexane dimethanol, ethylene oxide adduct of bisphenol A, glycerol,trimethylolpropane, pentaerythritol, dipentaerythritol and sorbitan.

Though not necessarily limited thereto only, preferred examples of thethermoplastic polyester include polyethylene terephthalate which is mostdesirable, as well as polyethylene/butylene terephthalate, polyethyleneterephthalate/2,6-naphthalate, polyethylene terephthalate/isophthalate,and the above compounds and polybutylene terephthalate, polybutyleneterephthalate/isophthalate, polyethylene-2,6-naphthalate, polybutyleneterephthalate/adipate, polyethylene-2,6-naphthalate/isophthalate,polybutylene terephthalate/adipate, and a blend of two or more kindsthereof.

The polyester should have a molecular weight in a range of forming afilm, and should have an inherent viscosity [IV] of not smaller than 0.5and, particularly, in a range of from 0.6 to 1.5 as measured by using aphenol/tetrachloroethane mixed solvent as a solvent, from the standpointof moldability, mechanical properties and heat resistance.

The polyester may contain at least one kind of reforming resin componentsuch as ethylene polymer, thermoplastic elastomer, polyarylate orpolycarbonate. It is desired that the reforming resin component is usedin an amount of up to 50 parts by weight and, particularly preferably,in an amount of from 5 to 35 parts by weight per 100 parts by weight ofthe polyester.

As the ethylene polymer, there can be exemplified low-, medium- orhigh-density polyethylene, linear low-density polyethylene, linearultra-low-density polyethylene, ethylene-propylene copolymer,ethylene-butene-1 copolymer, ethylene-propylene-butene-1copolymer,ethylene-vinyl acetate copolymer, ionically crosslinked olefin copolymer(ionomer) and ethylene-acrylic acid ester copolymer.

Among them, ionomer is preferred. As the base polymer of the ionomer,there can be used an ethylene-(meth)acrylic acid copolymer or anethylene-(meth)acrylic acid ester-(meth)acrylic acid copolymer. As thekind of ions, there can be used Na, K or Zn.

As the thermoplastic elastomer, there can be usedstyrene-butadiene-styrene block copolymer, styrene-isoprene-styreneblock copolymer, hydrogenated styrene-butadiene-styrene block copolymerand hydrogenated styrene-isoprene-styrene block copolymer.

The polyarylate can be defined as a polyester derived from a dihydricphenol and a dibasic acid. As the dihydric phenol, there can be usedbisphenols, such as 2,240 -bis(4-hydroxyphenyl)propane (bisphenol A),2,2′-bis(4-hydroxyphenyl)butane (bisphenol B),1,1′-bis(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl)methane (bisphenolF), 4-hydroxyphenyl ether and p-(4-hydroxy)phenol. Among them, bisphenolA and bisphenol B are preferred. As the dibasic acid, there can be usedterephthalic acid, isophthanol acid, 2,2-(4-carboxyphenyl)propane,4,4′-dicarboxydiphenyl ether, and 4,4′-dicarboxybenzophenone.

The polyarylate may be a homopolymer derived from the above monomericcomponent or may be a copolymer. Or, the polyarylate may be a copolymerof an aliphatic glycol with an ester unit derived from a dibasic acidwithin a range of not spoiling the essentials thereof. Thesepolyacrylates are available as U-series or AX-series of U-polymers ofUnitika Co., as Ardel D-100 of UCC Co., as APE of Bayer Co., as Durel ofHoechst Co., as Arylon of Du Pont Co. and as NAP resin of KanegafuchiKagaku Co.

The polycarbonate is a carbonic acid ester resin derived from bicyclicdihydric phenols and phosgene, and features a high glass transitionpoint and heat resistance.

As the polycarbonate, there can be used those derived from bisphenolssuch as 2,2′-bis(4-hydroxyphenyl)propane (bisphenol A),2,2′-bis(4-hydroxyphenyl)butane (bisphenol B),1,1′-bis(4-hydroxyphenyl)ethane, bis(4-hydroxyphenyl)methane (bisphenolF), 1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)cyclopentane,1,1-bis(4-hydroxyphenyl)-1-phenylmethane,1,1-bis(4-hydroxyphenyl)-1-phenylethane and1,2-bis(4-hydroxyphenyl)ethane.

The sheet used in the present invention may be blended with knownblending agents used for the plastics, such as antioxidant, heatstabilizer, ultraviolet-ray absorbing agent, antistatic agent, filler,coloring agent, etc. To make the molded container opaque, the sheet maybe blended with fillers such as calcium carbonate, calcium silicate,alumina, silica, various clays, calcined gypsum, talk or magnesia,inorganic pigments such as titanium white, yellow iron oxide, red ironoxide, ultramarine or chromium oxide, or organic pigments.

From the standpoint of strength and moldability of the container, it isdesired that the plastic sheet used in the present invention has athickness of, usually, from 0.5 to 5 mm and, particularly, from 1 to 3mm though it may vary depending upon the size of the container and thelike.

The container of the present invention may comprise the above singlepolyester layer or may comprise a laminated layer thereof with layers ofother resins such as gas-barrier resin, recycled polyester resin,oxygen-absorbing resin, etc.

The layers of other resins may be to form a two-layer constitutionserving as an inner layer or an outer layer, or to form a three-layerconstitution serving as an intermediate layer.

As the gas-barrier resin, there can be used any one that has been known,such as ethylene-vinyl alcohol copolymer (EVOH), nylon resin (Ny),gas-barrier polyester resin (BPR) or cyclic olefin copolymer.

As the gas-barrier resin layer, there can be used an ethylene-vinylalcohol copolymer containing a vinyl alcohol in an amount of from 40 to85 mol % and, particularly, from 50 to 80 mol %.

There is no particular limitation on the molecular weight of theethylene-vinyl alcohol copolymer provided it is large enough for forminga film. Generally, however, it is desired that the ethylene-vinylalcohol copolymer has an inherent viscosity (I.V.) in a range of from0.07 to 0.17 dl/g as measured in a mixed solvent of 85% by weight ofphenol and 15% by weight of water at a temperature of 30° C.

Other examples of the gas-barrier resin include nylon resin such asnylon 6, nylon 6,6, nylon 6/nylon 6,6 copolymer and polyamide containinga xylylene group.

As the ω-aminocarboxylic acid component constituting the nylon resin,there can be exemplified ε-caprolactam, aminoheptanoic acid andaminooctanoic acid. As the diamine component, there can be exemplifiedaliphatic diamines such as hexamethylene diamine, alicyclic diamine suchas piperazine, as well as m-xylylene diamine and/or p-xylylenediamine.As the dibasic acid component, there can be exemplified aliphaticdicarboxylic acids such as adipic acid, sebacic acid and suberic acid.As the aromatic dicarboxylic acid, there can be exemplified terephthalicacid and isophthalic acid.

In particular, there can be exemplified a polyamide having excellentbarrier property, in which not less than 35 mol % and, particularly, notless than 50 mol % of the diamine component is an m-xylylene and/or ap-xylylenediamine, and in which the dibasic component is an aliphaticdicarboxylic acid and/or an aromatic dicarboxylic acid and, as required,containing not more than 25 mol % and, particularly, not more than 20mol % of an ω-aminocarboxylic acid unit per the whole amide recurringunits.

It is desired that the polyamide that is used has a relative viscosity(ηrel) of from 0.4 to 4.5 as measured by using a sulfuric acid of 96% byweight at a concentration of 1 g/100 ml and at a temperature of 25° C.

As the gas-barrier resin, there can be used a gas-barrier polyester. Agas-barrier polyester (hereinafter often written as BPR) contains, in apolymer chain thereof, a terephthalic acid component (T) and anisophthalic acid component (I) at a molar ratio T:I of from 95:5 to 5:95and, particularly, from 75:25 to 25:75, and contains an ethylene glycolcomponent (E) and a bis(2-hydroxyethoxy)benzene component (BHEB) at aratio E:BHEB of from 99.999:0.001 to 2.0:98.0 and, particularly, from99.95:0.05 to 40:60.

As the BHEB, there is preferably used a 1,3-bis(2-hydroxyethoxy)benzene.

It is desired that the polyester (BPR) has a molecular weight which isat least large enough for forming a film and, generally, has an inherentviscosity [η] of from 0.3 to 2.8 dl/g and, particularly, from 0.4 to 1.8dl/g as measured in a mixed solvent of phenol and tetrachloroethane at aweight ratio of 60:40 at a temperature of 30° C.

As the recycled polyester (PCR), there can be used a granular or apowdery polyester obtained by recovering the used polyester containers,removing foreign matters therefrom, and washing and drying thepolyester. It is desired that the recycled polyester has an inherentviscosity (IV) in a range of from 0.60 to 0.75 as measured by theabove-mentioned method.

The recycled polyester can be used by itself or being blended with avirgin polyester. When the recycled polyester has a decreased inherentviscosity, it is desired to use the recycled polyester being blendedwith the virgin polyester. In this case, it is desired that the blendingratio of recycled polyester:virgin polyester is from 9:1 to 2:8.

It is desired that the recycled polyester (PCR) layer is used in amulti-layer structure having three or more layers being sandwiched bythe virgin polyesters.

As other resin layers, there can be used a layer of an oxygen-absorbingresin. As the layer of the oxygen-absorbing resin, there can be used theone containing a metallic oxidizing catalyst and an oxidizing organiccomponent.

The oxidizing organic component is a resin which is oxidized with oxygenin the air due to the catalytic action of a transition metal catalyst,i.e., (i) a resin containing a carbon side chain (a), and containing, inthe main chain or in the side chain thereof, at least one functionalgroup (b) selected from the group consisting of carboxylic acid estergroup, carboxylic acid amide group and carbonyl group, (ii) a polyamideresin, or (iii) an ethylene-type polymer containing an unsaturatedgroup.

As the metallic oxidizing catalyst, there can be exemplified metalcomponents of the Group VIII of periodic table, such as iron, cobalt andnickel, as well as metals of the Group I, such as copper and silver,metals of the Group IV, such as tin, titanium and zirconium, vanadiumwhich is of the Group V, chromium which is of the Group VI, andmanganese which is of the Group VII. Among these metal components,cobalt is particularly preferred because of its large oxygen-absorbingrate.

The transition metal catalysts are usually used in the form of inorganicacid salts or organic acid salts of the above transition metals havinglow valencies. It is desired that these catalysts are used in amounts offrom 100 to 1000 ppm in the resin.

The container of the present invention may include layers of any otherresins in addition to the above-mentioned polyester resin layer and thegas-barrier resin layer.

For example, when there is no heat adhesiveness between the polyesterlayer and the gas barrier resin layer, an adhesive resin layer may beinterposed between the above two resin layers.

Though there is no particular limitation, there can be used, as theadhesive resin, an acid-modified olefin resin such as maleicanhydride-grafted polyethylene, maleic anhydride-grafted polypropyleneand the like.

Referring to FIG. 7 illustrating, in cross section, the structure of amulti-layer plastic sheet, the sheet 2 has a laminated-layer structureincluding an inner layer 21 and an outer layer 22 of a thermoplasticpolyester resin, an intermediate layer 23 of a gas-barrier resin, andadhesive layers 24 and 25 which are, as required, provided for stronglyadhering the inner layer, the outer layer and the intermediate layer.

The laminated-layer sheet is preferably obtained by co-extruding theabove-mentioned thermoplastic polyester resin, the gas-barrier resinand, as required, the adhesive resin into the above-mentionedmulti-layer structure through a multi-layer multiple die. Thelaminated-layer sheet, however, can also be produced by any other layerlamination technology, such as sandwich lamination, extrusion coatingmethod or the like method.

EXAMPLES

The invention will now be described by way of working examples in whichmeasurement was taken in a manner as described below.

Measurement of Crystallinity.

As for the wall of the lower part of the barrel portion, a samplemeasuring 3 mm×3 mm was cut out from the thermoplastic polyester layer10 mm above the bottom surface of the container in the axial directionof the container. A sample measuring 3 mm×3 mm was also cut out from theflange portion. The densities of the samples were measured by using ann-heptane and a carbon tetrachloride density-gradient tube (Ikeda RikaCo.) at a temperature of 20° C.

The crystallinity Xc was calculated in compliance with the followingformula,Xc=(ρc/ρ)×(ρ−ρam)/(ρ−ρam)×100

-   -   ρ: density of the sample (g/cm³)    -   ρam: amorphous density (1.335 g/cm³)    -   ρc: crystalline density (1.455 g/cm³)        X-Ray Measurement.

As for the upper part of the wall of the barrel portion, a sample wascut out from the thermoplastic polyester layer 15 mm below the flangesurface in the axial direction of the container. As for the lower partof the wall of the barrel portion, the sample was cut out from thethermoplastic polyester layer 10 mm above the bottom surface of thecontainer in the axial direction of the container. The sample was so setthat the axial direction of the container was on the vertical axis ofthe optical coordinate, and the diffraction peak was measured by thetransmission method relying upon the micro X-ray diffraction (PSPC-150C)(manufactured by Rigaku Denki Co.).

The measurement was taken under the conditions of a tube voltage of 30KV, a tube current of 150 mA, a collimator of 100 μm and a measuringtime of 1000 seconds.

After the measurement, the background was removed (base line wascorrected) over a range of 2θ of from 10° to 35°, and a ratio ofdiffraction intensities was found on the planes (010) and (−110).

Drop Impact Strength.

The container was filled with 220 cc of water, and a closure memberhaving a polyester layer on the innermost surface thereof and the flangeportion of the container were heat-sealed by using a heat sealer(manufactured by Shinwa Kikai Co.) at a seal bar temperature of 230° C.for a sealing time of 2 seconds. After sealing, the container wasdropped on the concrete floor surface from a height of 90 cm with thebottom portion of the container being directed downward a maximum of 10times. The number n of the samples was 10, and average numbers until thesamples were broken were evaluated as follow: Average number of timesuntil broken Evaluation 8 to 10 times excellent 6 to 7 times good 4 to 5times acceptable 1 to 3 times badHeat Resistance.

The container was measured for its full volume, fully filled with thehot water of 70° C. and was left to stand until the temperature droppeddown to 30° C. The container was measured again for its full volume tofind a change in the volume before and after it was filled with the hotwater. The number n of the samples was 3, and the containers wereevaluated depending upon their changes in the volumes.

Change in the volume (%)=(full volume before fully filled−full volumeafter fully filled)/(full volume before fully filled)×100 Change in thevolume (%) Evaluation smaller than 0.5% excellent not smaller than 0.5%but smaller than 1% good not smaller than 1% but smaller than 2%acceptable not smaller than 2% bad

Example 1

A polyester was obtained by melt-kneading a thermoplastic polyester,RT-580CA (HOMO PET manufactured by Unipet Co.) by using a 65-mm extruder(manufactured by Nihon Seikosho Co.), and was extruded from a T-due of awidth of 400 mm and was quickly quenched to prepare a substantiallyamorphous sheet having a thickness of 1.2 mm. The sheet was cut into asquare of 30 cm, heated at 100° C. by a heater by using a plug-assistedcompressed air/vacuum molding machine (FK-0431 manufactured by AsanoKenkyujo Co.), and was held by an aluminum plug heated at 65° C. by aheater embedded therein and having a bottom area 84% of the bottom areaof the container and by a metal mold (female mold) heated at 110° C. bya heater mounted surrounding the metal mold. Thereafter, the compressedair was blown from the side of the plug for 10 seconds while evacuatingthe air from the side of the metal mold, in order to mold a transparentcontainer having a container diameter of 65 mm, a container height of100 mm and a volume of 235 cc.

Very good results were obtained concerning the crystallinity of the wallof the lower part of the barrel portion of the molded container,crystallinity of the flange portion, X-ray measurement of the upper andlower parts of the container, drop impact testing and heat resistance asshown in Table 1. Good heat resistance was further obtained even in theevaluation with the container being filled with the hot water of 90° C.

Example 2

A sheet was molded in the same manner as in Example 1 but using EFS-7H(HOMO PET manufactured by Kanebo Gosen Co.) as the thermoplasticpolyester to obtain a transparent container of the same shape. Very goodresults were obtained concerning the crystallinity of the wall of thelower part of the barrel portion of the molded container, crystallinityof the flange portion, X-ray measurement of the upper and lower parts ofthe container, drop impact testing and heat resistance as shown inTable 1. Good heat resistance was further obtained even in theevaluation with the container being filled with the hot water of 90° C.

Example 3

A sheet having a thickness of 1.2 mm was molded by using the RT-580CA asthe thermoplastic polyester in the same manner as in Example 1.Thereafter, a transparent container of the same shape was molded in thesame manner as in Example 1 but setting the metal mold temperature at80° C. in molding the container. Good results were obtained concerningthe crystallinity of the wall of the lower part of the barrel portion ofthe molded container, crystallinity of the flange portion, X-raymeasurement of the upper and lower parts of the container, drop impacttesting and heat resistance as shown in Table 1.

Example 4

A sheet having a thickness of 1.2 mm was molded by using the RT-580CA asthe thermoplastic polyester in the same manner as in Example 1.Thereafter, a transparent container of the same shape was molded in thesame manner as in Example 1 but using an aluminum plug heated at 65° C.by a heater embedded therein and having a bottom area 84% of the bottomarea of the container and having a shoulder portion for molding theflange and by using a metal mold heated at 110° C. by a heater mountedsurrounding the metal mold and having a flange-molding portion in acavity thereof in molding the container. Very good results were obtainedconcerning the crystallinity of the wall of the lower part of the barrelportion of the molded container, crystallinity of the flange portion,X-ray measurement of the upper and lower parts of the container, dropimpact testing and heat resistance as shown in Table 1. Good heatresistance was further obtained even in the evaluation with thecontainer being filled with the hot water of 90° C.

Example 5

A three-kind-five-layer sheet having a thickness of 1.2 mm was molded byusing J125T (manufactured by Mitsui Kagaku Co.) as a thermoplasticpolyester of inner and outer layers, Evar EP-F101B (manufactured byKuraray Co.) as an intermediate layer and Modec F512 (manufactured byMitsubishi Kagaku Co.) as an adhesive among the intermediate layer andthe polyester layers, through the use of a multi-layer sheet-moldingmachine. Then, the sheet was molded in the same manner as in Example 1to obtain a container of the same shape. Very good results were obtainedconcerning the crystallinity of the wall of the lower part of the barrelportion of the molded container, crystallinity of the flange portion,X-ray measurement of the upper and lower parts of the container, dropimpact testing and heat resistance as shown in Table 1. Good heatresistance was further obtained even in the evaluation with thecontainer being filled with the hot water of 90° C.

Comparative Example 1

A sheet having a thickness of 1.2 mm was molded by using RT-580CA(manufactured by Unipet Co.) as a thermoplastic polyester through theuse of a sheet-molding machine in the same manner as in Example 1. Then,a container of the same shape was molded in the same manner as inExample 1 but heating the sheet again at 130° C. in molding thecontainer. The crystallinity of the wall of the lower part of the barrelportion of the molded container, crystallinity of the flange portion,X-ray measurement of the upper and lower parts of the container, dropimpact testing and heat resistance were as shown in Table 1, from whichit was learned that the impact resistance and heat resistance wereinferior.

Comparative Example 2

A sheet having a thickness of 1.2 mm was molded by using RT-580CA(manufactured by Unipet Co.) as a thermoplastic polyester through theuse of a sheet-molding machine in the same manner as in Example 1. Then,a container of the same shape was molded in the same manner as inExample 1 but using an aluminum plug heated at 110° C. by a heaterembedded therein and having a bottom area 84% of the bottom area of thecontainer in molding the container. The crystallinity of the wall of thelower part of the barrel portion of the molded container, crystallinityof the flange portion, X-ray measurement of the upper and lower parts ofthe container, drop impact testing and heat resistance were as shown inTable 1, from which it was learned that the impact resistance wasinferior.

Comparative Example 3

A sheet having a thickness of 1.2 mm was molded by using RT-580CA(manufactured by Unipet Co.) as a thermoplastic polyester through theuse of a sheet-molding machine in the same manner as in Example 1. Then,a container of the same shape was molded in the same manner as inExample 1 but using an aluminum plug heated at 65° C. by a heaterembedded therein and having a bottom area 65% of the bottom area of thecontainer in molding the container. The crystallinity of the wall of thelower part of the barrel portion of the molded container, crystallinityof the flange portion, X-ray measurement of the upper and lower parts ofthe container, drop impact testing and heat resistance were as shown inTable 1, from which it was learned that the impact resistance wasinferior.

Comparative Example 4

A sheet having a thickness of 1.2 mm was molded by using RT-580CA(manufactured by Unipet Co.) as a thermoplastic polyester through theuse of a sheet-molding machine in the same manner as in Example 1. Then,a container of the same shape was molded in the same manner as inExample 1 but setting the metal mold temperature at 20° C. in moldingthe container. The crystallinity of the wall of the lower part of thebarrel portion of the molded container, crystallinity of the flangeportion, X-ray measurement of the upper and lower parts of thecontainer, drop impact testing and heat resistance were as shown inTable 1, from which it was learned that the impact resistance and heatresistance were very inferior.

Comparative Example 5

A sheet having a thickness of 1.2 mm was molded by using RT-580CA(manufactured by Unipet Co.) as a thermoplastic polyester through theuse of a sheet-molding machine in the same manner as in Example 1. Then,a container of the same shape was molded in the same manner as inExample 1 but setting the metal mold temperature at 60° C. in moldingthe container. The crystallinity of the wall of the lower part of thebarrel portion of the molded container, crystallinity of the flangeportion, X-ray measurement of the upper and lower parts of thecontainer, drop impact testing and heat resistance were as shown inTable 1, from which it was learned that the impact resistance and heatresistance were inferior.

Comparative Example 6

A container having the same shape was molded in the same manner as inExample 1 but using (Eastapak polyester 15041, (manufactured by EastmanCo.) which is used for a C-PET tray) as a thermoplastic polyester. Thecrystallinity of the wall of the lower part of the barrel portion of themolded container, crystallinity of the flange portion, X-ray measurementof the upper and lower parts of the container, drop impact testing andheat resistance were as shown in Table 1, from which it was learned thatthe heat resistance was excellent but the impact resistance was veryinferior. TABLE 1 Barrel wall Flange crystal- crystal- X-ray measurementDrop linity linity Formula Formula Formula impact Heat (%) (%) (1) (2)(3) strength resistance Ex. 1 29 2.8 0.87 0.45 0.42 excellent excellentEx. 2 30 3.1 0.72 0.33 0.29 excellent excellent Ex. 3 18 2.6 1.01 0.750.26 good acceptable Ex. 4 29 24.3 0.85 0.42 0.43 excellent excellentEx. 5 30 2.7 0.79 0.37 0.42 excellent excellent Comp. Ex. 1 12 2.6 1.041.09 −0.05 bad bad Comp. Ex. 2 15 2.7 1.06 0.99 0.07 bad acceptableComp. Ex. 3 13 2.6 0.85 1.01 −0.16 bad acceptable Comp. Ex. 4 12 2.6 1.21.08 0.12 bad bad Comp. Ex. 5 13 2.6 1.07 1 0.07 bad bad Comp. Ex. 6 3025 1.02 0.95 0.07 bad excellentwherein:Formula (1): Iu(−110)/Iu(010)Formula (2): IL(−110)/IL(010)Formula (3): Iu(−110)/Iu(010) − IL(−110)/IL(010)

Example 6

A polyethylene terephthalate having an inherent viscosity of 0.80 and aglass transition point of 70° C. was melt-extrusion-molded to obtain asubstantially amorphous sheet having a thickness of 1.2 mm. The sheetwas heated at a sheet temperature of 95° C. and was supplied to themolding device shown in FIG. 8. The sheet was held by the holdingsurfaces of the female mold and of the clamping mold, and was stretchedin the axial direction by a plug heated at 75° C., having an effectivediameter of 69 mm, having an effective height of 86 mm, and having asurface area which was 6.2 times as wide as the to-be-molded area of thesheet, thereby to obtain a primary molded article.

The compressed air of 0.6 MPa was blown into the interior of the primarymolded article through the gas passage of the plug to form and heat-seta secondary molded article in the female mold heated at 150° C. by thecompressed air.

Next, the pressure in the interior of the secondary molded article wasreduced by a vacuum pump through the gas passage of the plug to shape itinto a tertiary molded article which was, then, cooled and taken out toobtain a final molded article. The finally molded article was evaluatedin a manner as described below.

-   -   {circle over (1)} Samples for measurement, each measuring 4 mm×4        mm, were cut out from the bottom portion (A) of the molded        article shown in FIG. 19, from a measuring center (B) 30 mm        above the bottom, from a measuring center (C) 55 mm above the        bottom, from a measuring center of the stacking portion (D) and        from a measuring center of the flange portion (E). Each sample        was sliced into the inner surface side and into the outer        surface side of the container along a neutral plane.        Crystallinities on the inner surface side and on the outer        surface side at each of the measuring points were measured        relying upon the density method.    -   {circle over (2)} The molded article was left to stand in a        temperature-controlled oven so that the temperature of the side        wall of the molded article became 90° C. for 3 minutes. The full        volume of the molded article was measured before it was put into        the oven and after it was taken out from the oven. A change in        the volume was calculated in compliance with the following        formula to evaluate the heat resistance of the molded article,        -   Change in the volume (%)=[(full volume before put into the            oven)−(full volume after taken out from the oven)]/(full            volume before put into the oven)×100    -   {circle over (3)} The molded article was filled with 200 ml of        water, and the mouth was heat-sealed with a closure member to        obtain a sample for evaluation. The sample was dropped on the        concrete surface from a height of 90 cm in such a manner that        the axis of the container was in parallel with the concrete        surface. The sample was repetitively dropped until it was        broken, and the impact resistance was evaluated based on the        number of times until it was broken.    -   {circle over (4)} The transparency of the whole container was        evaluated by naked eyes.

The results of evaluation were as shown in Table 2 from which it waslearned that the container obtained by the molding method of the presentinvention exhibited both excellent heat resistance and excellent impactresistance, and was transparent over the whole container except theflange.

Example 7

A polyethylene terephthalate having an inherent viscosity of 0.80 and aglass transition point of 70° C. was used as an inner layer and an outerlayer, a polymethaxyleneadipamide (MXD6) was used as an intermediatelayer, and a maleic acid-modified ethylene-α-olefin copolymer wasinterposed as adhesive layers among the inner layer, the outer layer andthe intermediate layer. The laminate of these layers wasmelt-extrusion-molded to obtain a substantially amorphous 5-layer sheethaving a thickness of 1.2 mm. The sheet was molded under the sameconditions as in Example 6 to obtain a finally molded article which was,then, evaluated in the same manner as in Example 6.

The results of evaluation were as shown in Table 2 from which it waslearned that the container obtained by molding the multi-layer sheet bythe molding method of the present invention, too, exhibited bothexcellent heat resistance and excellent impact resistance, and wastransparent over the whole container except the flange.

Example 8

A polyethylene terephthalate having an inherent viscosity of 0.80 and aglass transition point of 70° C. was melt-extrusion-molded to obtain asubstantially amorphous sheet having a thickness of 1.2 mm. The sheetwas heated at a sheet temperature of 95° C. and was supplied to themolding device shown in FIG. 8. The sheet was held by the holdingsurfaces of the female mold and of the clamping mold, and was stretchedin the axial direction by a plug heated at 80° C., having an effectivediameter of 69 mm, having an effective height of 86 mm, and having asurface area which was 6.2 times as wide as the to-be-molded area of thesheet, thereby to obtain a primary molded article.

The compressed air of 0.6 MPa was blown into the interior of the primarymolded article through the gas passage of the plug to form a secondarymolded article in the female mold heated at 50° C. by the compressedair, followed by shaping, cooling and parting to obtain an intermediatearticle (first step in the two-step molding method).

Then, the intermediate article was supplied into the molding deviceshown in FIG. 14 to effect the second step in the two-step moldingmethod.

The plug used in the second step was heated at 50° C. and the femalemold was heated at 150° C. The plug possessed an outer shape which wassuch that the effective diameter was 64 mm, the effective height was 51mm and the surface area was 4.2 times as wide as the to-be-molded areaof the sheet. The intermediate article supported by the plug wasinserted in the female mold, the compressed air of 0.6 MPa was blownthrough the gas passage of the plug to form a secondary molded articlein the heated female mold and to heat-set the secondary molded article.

Next, the pressure in the interior of the secondary molded article wasreduced by a vacuum pump through the gas passage of the plug to shape itinto a tertiary molded article which was, then, cooled and taken out toobtain a final molded article. The finally molded article was evaluatedin the same manner as in Example 6.

The results of evaluation were as shown in Table 2 from which it waslearned that the container obtained by the two-step molding method ofthe present invention, too, exhibited both excellent heat resistance andexcellent impact resistance, and was transparent over the wholecontainer except the flange.

Comparative Example 7

A polyethylene terephthalate having an inherent viscosity of 0.80 and aglass transition point of 70° C. was melt-extrusion-molded to obtain asubstantially amorphous sheet having a thickness of 1.2 mm. The sheetwas heated at a sheet temperature of 95° C. and was supplied to awidely-known compressed-air molding device (prior art 2). The plug(cooling type) used in the known compressed-air molding was heated at120° C. as described in the known literature, and the female mold(heating type) was heated at 220° C. The plug and the female moldpossessed such outer shapes that the effective diameter was 69 mm, theeffective height was 86 mm, and the surface area was 6.2 times as wideas the to-be-molded area of the sheet. The conditions were the same asthose of Example 6 except the heating temperature.

The sheet was sandwiched by the plug and the female mold that fitted toeach other, molded by the compressed air and was heat-set. Immediatelythereafter, the compressed air was blown through the gas passage of thefemale mold to shape the molded article along the plug. The moldedarticle was then parted. The thus obtained finally molded article wasevaluated in the same manner as in Example 6.

The results of evaluation were as shown in Table 2, from which it waslearned that the container obtained by the above molding methodexhibited excellent heat resistance but very poor impact resistance andtransparency. TABLE 2 Item evaluated Example 6 Example 7 Example 8 Comp.Example 7 {circle over (1)} Crystallinity % outer inner outer innerouter inner outer inner Measuring point surface surface surface surfacesurface surface surface surface A 28.0 18.5 28.1 18.3 25.2 16.7 42.037.8 B 31.2 27.9 31.3 28.0 28.1 25.1 46.8 41.8 C 36.0 29.9 35.6 31.232.4 26.9 44.5 44.9 D 33.4 30.5 33.2 30.7 30.1 27.5 44.4 45.8 E 27.1 4.026.3 4.0 24.4 3.6 40.7 42.4 {circle over (2)} Change in volume (%) 0.50.6 0.7 0.9 {circle over (3)} Note¹⁾ Drop testing ◯ ◯ ◯ X {circle over(4)} Note²⁾ Transparency ◯ ◯ ◯ XNote¹⁾ X represents the containers that were broken in the drop testingof 1 to 4 times, and ◯ represents the containers that were not broken.Note²⁾ ◯ represents the containers that were judged by three monitors tobe transparent, Δ represents the containers that were judged to containopaque portions, and X represents the containers that were judged to beopaque.

Example 9

By using a sheet-molding machine, a polyethylene terephthalate resin(SA135 manufactured by Mitsui Kagaku Co.) was melt-extrusion molded toprepare a substantially amorphous sheet having a thickness of 1.2 mm anda width of 320 mm. The sheet was cut into a square of 300 mm and washeated at 95° C. by using a compressed air/vacuum molding machine(FK-0431 manufactured by Asano Kenkyujo Co.). Then, the metal mold wastightened, and the plug heated at 50° C. was driven by an air cylinderin a state where the sheet was held by the holding surfaces of thefemale mold for pre-molding heated by a heater at 100° C. and of theclamping method, in order to mold the sheet in the solid phase. At thesame time, the compressed air of 0.6 MPa was blown from the side of theplug to prepare a pre-molded article having a diameter of 66 mm and asurface area of 159 cm².

At a next step, the pre-molded article was held by the female mold forpre-molding heated at 180° C. and by the clamping mold, and the pressureon the side of the plug was reduced in a state where the plug wasinserted in the pre-molded article, the plug being heated at 110° C. andhaving the shape nearly the same as the shape of the inner surface ofthe container. The pre-molded article was heated and shrunk by heatradiated from the female mold so as to come into intimate contact withthe surface of the plug, thereby to form an intermediate article havingthe shape nearly the same as the shape of the container and having adiameter of 66 mm and a surface area of 130 cm². Table 3 shows the ratioof the surface areas of the pre-molded article and of the intermediatearticle.

At a next step, the intermediate article was held by the clamping moldand by the female mold for final molding heated at 180° C. higher thanthe crystallization start temperature of the polyethylene terephthalateresin. Then, the compressed air of 0.6 MPa was blown from the side ofthe plug to heat-set the intermediate article while it was beingintimately adhered to the female mold. Thereafter, the pressure on theside of the plug was reduced in a state where the plug heated at 90° C.and having a shape nearly the same as the shape of the inner surface ofthe container was inserted in the intermediate article, so that theintermediate article was intimately adhered onto the surface of the plugto thereby shape the container. At the same time, the container wascooled down to the plug temperature and was, then, taken out.Thereafter, the periphery of the flange was trimmed to obtain asubstantially transparent container having a container diameter of 66mm, a container height of 53 mm and a volume of 158 cc.

The container was evaluated in a manner as described below.

1. Heat Resistance.

An empty container after its full volume was measured, was heat-treatedin the hot water of 90° C. for 30 minutes, taken out from the hot water,left to cool down to room temperature, and was measured again for itsfull volume. A change in the volume before and after the heat treatmentwas found from the following formula, and the heat resistance wasevaluated as described below.Change  in  the  volume  (%) = (full  volume  before  the  heat  treatment − full  volume  after  the  heat  treatment)/(full  volume  before  the  heat  treatment) × 100Change in the volume (%) Evaluation smaller than 1.0% excellent notsmaller than 1% but smaller than 2% good not smaller than 2% but smallerthan 4% acceptable not smaller than 4% bad2. Impact Strength.

The container was fully filled with water, and a closure member having apolyester layer on the innermost surface thereof and the flange portionof the container were heat-sealed by using a heat sealer (manufacturedby Shinwa Kikai Co.) at a seal bar temperature of 230° C. After sealing,the container was dropped on the concrete floor surface from a height of90 cm with the bottom portion of the container being directed downward amaximum of 10 times. The number n of the samples was 10, and averagenumbers until the samples were broken were evaluated as follows: Averagenumber of times until broken Evaluation 8 to 10 times excellent 6 to 7times good 4 to 5 times acceptable 1 to 3 times bad3. Transparency.

The transparency of the whole container was evaluated by naked eyes.

The container was evaluated for its transparency, heat resistance andimpact resistance to be all excellent as shown in Table 3.

Example 10

A pre-molded article and an intermediate article of the same shape wereprepared from the polyethylene terephthalate resin (SA135 manufacturedby Mitsui Kagaku Co.) in the same manner as in Example 9.

At a next step, the intermediate article has held by the clamping moldand the female mold for final molding heated at 130° C. higher than thecrystallization start temperature of the polethylene terephthalateresin, and a substantially transparent container having the same shapewas prepared in the same manner as in Example 9.

The container was evaluated for its transparency, heat resistance andimpact resistance to be all excellent as shown in Table 3.

Example 11

A substantially transparent container having the same shape was obtainedin the same manner as in Example 9 with the exception of forming, byusing a multi-layer sheet-molding machine, a three-kind-five-layer sheetcomprising inner and outer layers of a polyethylene terephthalate resin(J125T manufactured by Mitsui Kagaku Co.), an intermediate layer of apolymethaxyleneadipamide (MXD6,6007 manufactured by Mitsubishi GasKagaku Co.), and adhesive layers of an acid-modified ethylene-butenecopolymer (Modic F512 manufactured by Mitsubishi Kagaku Co.) among theintermediate layer and the inner and outer layers, having a thickness of1.2 and a width of 320 mm, the polyethylene terephthalate layers beingsubstantially amorphous.

The container was evaluated for its transparency, heat resistance andimpact resistance to be all excellent as shown in Table 3. The barrierproperty was favorable, too.

Example 12

By using a multi-layer sheet-molding machine, there was prepared atwo-kind-three-layer sheet comprising inner and outer layers of apolyethylene terephthalate resin (SA135 manufactured by Mitsui KagakuCo.), and an intermediate layer of a recycled polyethylene terephthalate(Clear-Flake manufactured by Yono PET Bottle Recycle Co.), having athickness of 1.2 and a width of 320 mm. An intermediate article and asubstantially transparent container of the same shape were prepared inthe same manner as in Example 9 except that the pre-molded articleprepared from the above sheet possessed such a shape as a diameter of 66mm and a surface area of 185 cm².

The container was evaluated for its transparency, heat resistance andimpact resistance to be all excellent as shown in Table 3.

Example 13

A pre-molded article of the same shape was prepared from thepolyethylene terephthalate resin (SA135 manufactured by Mitsui KagakuCo.) in the same manner as in Example 9.

At a next step, the pre-molded article has held by the clamping mold andthe female mold for intermediate molding heated at 180° C., and thepre-molded article was heated and shrunk by heat radiated from thefemale mold without inserting the plug thereby to obtain an intermediatearticle having a diameter of 66 mm and a surface area of 120 cm². Theratio of surface areas of the pre-molded article and of the intermediatearticle was as shown in Table 3.

Next, a substantially transparent container having a container diameterof 66 mm, a container height of 53 mm and a volume of 158 cc wasobtained from the above intermediate article in the same manner as inExample 9.

The container was evaluated for its transparency, heat resistance andimpact resistance to be all excellent as shown in Table 3.

Comparative Example 8

A sheet was prepared from the polyethylene terephthalate resin (SA135manufactured by Mitsui Kagaku Co.) in the same manner as in Example 9. Apre-molded article was prepared in the same manner as in Example 9except that the pre-molded article prepared from the sheet possessed adiameter of 66 mm and a surface area of 199 cm².

At a next step, the pre-molded article has heat-shrunk in the samemanner as in Example 9. However, the pre-molded article did not shrinkto a sufficient degree, i.e., did not shrink to the shape of the plug,and there was obtained no intermediate article.

Comparative Example 9

A sheet was prepared from the polyethylene terephthalate resin (SA135manufactured by Mitsui Kagaku Co.) in the same manner as in Example 9.An intermediate article and a container were prepared in the same manneras in Example 9 except that the pre-molded article prepared from thesheet possessed a diameter of 66 mm and a surface area of 135 cm².

The container was evaluated for its transparency, heat resistance andimpact resistance as shown in Table 3, from which it was learned thatthe bottom portion of the container had been whitened deteriorating thetransparency and the impact resistance was inferior, either.

Comparative Example 10

A pre-molded article and an intermediate article of the same shape wereprepared from the polyethylene terephthalate resin (SA135 manufacturedby Mitsui Kagaku Co.) in the same manner as in Example 9.

At a next step, the intermediate article was held by the clamping moldand the female mold for final molding heated at 90° C. lower than thecrystallization start temperature of the polyethylene terephthalateresin, and a substantially transparent container having the same shapewas prepared in the same manner as in Example 9.

The container was evaluated for its transparency, heat resistance andimpact resistance as shown in Table 3, from which it was learned thatthe heat resistance was inferior. TABLE 3 Surface area of pre-moldedarticle/ surface area of Heat Impact intermediate article Transparencyresistance resistance Example 9 1.22 transparent excellent excellentExample 10 1.22 transparent good excellent Example 11 1.22 transparentexcellent excellent Example 12 1.42 transparent excellent good Example13 1.33 transparent excellent excellent Comp. Ex. 8 1.53 container couldnot be formed Comp. Ex. 9 1.04 bottom whitened excellent bad Comp. Ex.10 1.22 transparent bad excellent

Example 14

A polyethylene terephthalate resin (SA135, I.V.=0.8, manufactured byMitsui Kagaku Co.) was melt-extrusion molded to prepare a substantiallyamorphous sheet having a thickness of 1.2 mm and a width of 320 mm. Thesheet was cut into a square of 300 mm and was heated at 95° C. by usinga compressed air/vacuum molding machine (FK-0431 manufactured by AsanoKenkyujo Co.). Then, the metal mold was tightened, and the plug heatedat 75° C. and having the shape of the inner surface of the container wasdriven by an air cylinder in a state where the sheet was held by theholding surfaces of the female mold heated by a heater at 80° C. and ofthe clamping mold, in order to stretch-mold the sheet. At the same time,the compressed air of 0.6 MPa was blown from the side of the plug sothat the stretch-molded article was intimately adhered to the femalemold and was heat-set. Next, the pressure on the side of the plug wasreduced so that the stretch-molded article was intimately adhered ontothe surface of the plug and was shaped. The stretch-molded article wasthen cooled down to the plug temperature and, then, the metal mold wasopened. Thereafter, the periphery of the flange was trimmed to obtain asubstantially transparent container having a container diameter of 66mm, a container height of 100 mm and a volume of 256 cc.

The container was evaluated in a manner as described below.

1. Heat Resistance.

An empty container after its full volume was measured, was put into adry-heating oven heated at 150° C. and was heat-treated therein in astate where the container wall was heated at 100° C. for 10 seconds andwas, then, taken out, and was cooled down to room temperature. Thecontainer was measured again for its full volume. A change in the volumebefore and after the heat treatment was found from thefollowing-formula, and the heat resistance was evaluated as describedbelow.Change  in  the  volume  (%) = (full  volume  before  the  heat  treatment − full  volume  after  the  heat  treatment)/(full  volume  before  the  heat  treatment) × 100Change in the volume (%) Evaluation smaller than 1.0% excellent notsmaller than 1% but smaller than 2% good not smaller than 2% but smallerthan 4% acceptable not smaller than 4% bad2. Impact Strength.

The container was fully filled with water, and a closure member having apolyester layer on the innermost surface thereof and the flange portionof the container were heat-sealed by using a heat sealer (manufacturedby Shinwa Kikai Co.) at a sealing temperature of 230° C. After sealing,the container was dropped on the concrete floor surface from a height of90 cm with the bottom portion of the container being directed downward amaximum of 10 times. The number n of the samples was 10, and averagenumbers until the samples were broken were evaluated as follows: Averagenumber of times until broken Evaluation 8 to 10 times excellent 6 to 7times good 4 to 5 times acceptable 1 to 3 times bad

The container was evaluated for its crystallinity at the center in thebottom portion and on the side wall thereof, X-ray diffractionmeasurement thereof, transparency, strength in the drop impact testingand heat resistance as shown in Table 4, from which it was learned thatexcellent heat resistance and impact resistance were exhibited.

Example 15

By using a multi-layer sheet-molding machine, there was prepared athree-kind-five-layer sheet comprising inner and outer layers of apolyethylene terephthalate resin (J125T manufactured by Mitsui KagakuCo.), an intermediate layer of an ethylene-vinyl alcohol copolymer (EvarEP-F101B manufactured by Kuraray Co.), and adhesive layers of anacid-modified ethylene-butene copolymer (Modic F512 manufactured byMitsubishi Kagaku Co.) among the intermediate layer and the inner andouter layers, having a thickness of 1.2 and a width of 320 mm, thepolyethylene terephthalate layers being substantially amorphous.Thereafter, a container was molded in the same manner as in Example 14to obtain a container of the same shape having a substantiallytransparent bottom portion.

The container was evaluated for its crystallinity at the center in thebottom portion and on the side wall thereof, X-ray diffractionmeasurement thereof, transparency, strength in the drop impact testingand heat resistance as shown in Table 4, from which it was learned thatexcellent heat resistance and impact resistance were exhibited. Thegas-barrier property of the container was also evaluated to beexcellent.

Example 16

By using a multi-layer sheet-molding machine, there was prepared atwo-kind-three-layer sheet comprising inner and outer layers of apolyethylene terephthalate resin (SA135 manufactured by Mitsui KagakuCo.), and an intermediate layer of a recycled polyethylene terephthalate(Clear-Flake, manufactured by Yono PET Bottle Recycle Co.), having athickness of 1.2 and a width of 320 mm. Thereafter, a container wasmolded in the same manner as in Example 14 to obtain a container of thesame shape having a substantially transparent bottom portion.

The container was evaluated for its crystallinity at the center in thebottom portion and on the side wall thereof, X-ray diffractionmeasurement thereof, transparency, strength in the drop impact testingand heat resistance as shown in Table 4, from which it was learned thatexcellent heat resistance and impact resistance were exhibited.

Example 17

By using a multi-layer sheet-molding machine, there was prepared athree-kind-five-layer sheet comprising inner and outer layers of apolyethylene terephthalate resin (J125T manufactured by Mitsui KagakuCo.), an intermediate layer of a polymethaxyleneadipamde (MXD6,6007manufactured by Mitsubishi Gas Kagaku Co.), adhesive layers of anacid-modified ethylene-butene copolymer (Modic F512 manufactured byMitsubishi Kagaku Co.) among the intermediate layer and the inner andouter layers, having a thickness of 1.2 and a width of 320 mm, thepolyethylene terephthalate layers being substantially amorphous. Thesheet was cut into a square of 300 mm and was heated at 95° C. by usinga compressed air/vacuum molding machine (FK-0431 manufactured by AsanoKenkyujo Co.). Then, the metal mold was tightened, and the plug heatedat 50° C. was driven by an air cylinder in a state where the sheet washeld by the holding surfaces of the female mold for pre-molding heatedby a heater at 100° C. and of the clamping mold, in order tostretch-mold the sheet. At the same time, the compressed air of 0.6 MPawas blown from the side of the plug to prepare a pre-molded articlehaving a diameter of 66 mm and a surface area of 159 cm².

At a next step, the pre-molded article was held by the female mold forintermediate molding heated at 180° C. and by the clamping mold, and thepressure on the side of the plug was reduced in a state where the plugwas inserted in the pre-molded article, the plug being heated at 110° C.and having the shape nearly the same as the shape of the inner surfaceof the container. The pre-molded article was heated and shrunk by heatso as to come into intimate contact with the surface of the plug,thereby to form an intermediate article having the shape nearly the sameas the shape of the container and having a diameter of 66 mm and asurface area of 130 cm². The ratio of the surface areas of thepre-molded article and of the intermediate article was 1.22.

At a next step, the intermediate article was held by the clamping moldand by the female mold for final molding heated at 180° C. Then, thecompressed air of 0.6 MPa was blown from the side of the plug toheat-set the intermediate article while it was being intimately adheredto the female mold. Thereafter, the pressure on the side of the plug wasreduced in a state where the plug heated at 90° C. and having a shapenearly the same as the shape of the inner surface of the container wasinserted in the intermediate article, so that the intermediate articlewas intimately adhered onto the surface of the plug to thereby shape thecontainer. At the same time, the container was cooled down to the plugtemperature and was, then, taken out. Thereafter, the periphery of theflange was trimmed to obtain a container having a container diameter of66 mm, a container height of 53 mm and a volume of 158 cc with itsbottom portion being substantially transparent.

The container was evaluated for its crystallinity at the center in thebottom portion and on the side wall thereof, X-ray diffractionmeasurement thereof, transparency, strength in the drop impact testingand heat resistance as shown in Table 4, from which it was learned thatexcellent heat resistance and impact resistance were exhibited. Thecontainer further exhibited favorable heat resistance even after it washeat-treated in the hot water of 90° C. for 30 minutes. The containerfurther exhibited excellent gas-barrier property.

Comparative Example 11

A sheet was prepared in the same manner as in Example 14, and acontainer of the same shape having a substantially transparent bottomportion was obtained under the same conditions as in Example 14 butheating the female mold at 60° C.

The container was evaluated for its crystallinity at the center in thebottom portion and on the side wall thereof, X-ray diffractionmeasurement thereof, transparency, strength in the drop impact testingand heat resistance as shown in Table 4, from which it was learned thatexcellent impact resistance was exhibited but the heat resistance wasinferior.

Comparative Example 12

A sheet was prepared in the same manner as in Example 14, and acontainer of the same shape was obtained under the same conditions as inExample 14 but heating the sheet at 120° C.

The center in the bottom portion of the container was substantiallytransparent but was slightly cloudy.

The container was evaluated for its crystallinity at the center in thebottom portion and on the side wall thereof, X-ray diffractionmeasurement thereof, transparency, strength in the drop impact testingand heat resistance as shown in Table 4, from which it was learned thatexcellent heat resistance was exhibited but the impact resistance wasinferior. TABLE 4 Crystallinity Crystallinity Orienta- at bottom ofbarrel tion Heat Impact center (%) portion (%) tendency Transparencyresistance resistance Example 14 31 39 1.5 transparent excellentexcellent Example 15 29 38 1.3 transparent excellent excellent Example16 31 38 1.4 transparent excellent good Example 17 35 37 2 transparentexcellent excellent Comparative 11 19 1 transparent bad excellentExample 11 Comparative 30 35 1.2 bottom is excellent bad Example 12slightly cloudy

Examples 18, 19 and Comparative Example 13 were evaluated as describedbelow.

[Stacking Performance]

1. Overlapping Amount.

The overlapping amount is expressed by (a maximum diameter−a minimumdiameter) of the portions used for the stacking, and is either one ofthe following value (i) or (ii) whichever is larger. The overlappingamount which is not smaller than 0.5 mm is acceptable ◯ and which issmaller than 0.5 mm is not acceptable X.

-   -   (i) (Outer diameter of stack portion−inner diameter of bead        portion)/2    -   (ii) (Outer diameter of stack portion−inner diameter of mouth        portion)/2        2. Stack Falling Test.

A stack of 40 containers is caused to fall from a height equal to thestack of 40 containers to evaluate if they can be separated. The stackthat can be separated is regarded to be acceptable ◯ and the stack thatcannot be separated is regarded to be not acceptable X.

[Rigidity]

The stacking portion is crushed through the flange by using a press witha load meter from a direction perpendicular to the direction of the axisof the cup, and the load is measured when the amount of deformationbecomes 20% of the initial amount.

The measuring amount of not smaller than 70 N is regarded to beacceptable ◯ and of smaller than 70 N is regarded to be not acceptableX.

Example 18

A polyethylene terephthalate resin (SA 135 manufactured by Mitsui KagakuCo., containing 2 mol % of isophthalic acid) having an inherentviscosity of 0.8 dL/g was fed to an injection-molding machine (NN75JSmanufactured by Niigata Tekkojo Co.) and was injection-molded under theconditions of an injection temperature of 275 to 300° C. and aninjection pressure of 10 kg/cm² to obtain 15.6 g of a substantiallyamorphous molding precursor (preform) of a single layer.

The flange portion of the preform was heated by the irradiation from anear infrared ray heater up to 180° C. to crystallize.

The preform was heated at 95° C. which was higher than the glasstransition point, the flange portion was held by the upperflange-forming mold (hereinafter referred to as UFM, 30° C.) and thelower flange-forming mold (hereinafter referred to as LFM, 30° ) with amold-fastening force of 10 kN, and the interior of the flange wasstretch-molded by using a plug (75° C.) having the outer surface shapethat becomes the inner surface shape of the final molded article andhaving a bead shape between the flange portion and the stacking portion.Then, the preform was blow-molded (1.3 MPa) onto the female metal moldheated at 180° C. which was not smaller than the crystallizationinitiating temperature so as to be heat-set, and was shrunk back intothe shape of the plug being assisted by the blow (1.3 Mpa) from thefemale mold and by the vacuum from the plug, thereby to obtain acup-like container with a flange.

Portions where the cup-like container was measured for its size were asshown in FIG. 33 and the portions where the molding tools were measuredfor their sizes were as shown in FIG. 45. The sizes and evaluatedresults were as shown in Table 5. The stacking performance and therigidity were both of practically satisfactory levels.

Example 19

A polyethylene terephthalate resin (SA 135 manufactured by Mitsui KagakuCo., containing 2 mol % of isophthalic acid) having an inherentviscosity of 0.8 dL/g was fed to an extruder. A molten and kneadedpolyester was extruded through a T-die and was quickly cooled to obtaina substantially amorphous sheet of a single layer having a thickness of2.5 mm.

The sheet was cut into a square of 30 cm and was heated by theirradiation from an infrared ray heater up to 95° C. which was notsmaller than the glass transition point thereof.

By using the UFM (90 ° C.) and the LFM (180° ), the sheet was held witha mold-fastening force of 10 kN to obtain a crystallized flange portion.

Next, the interior of the flange portion was molded in the same manneras in Example 18 to obtain a cup-like container with a flange.

The sizes and evaluated results were as shown in Table 5. The stackingperformance and the rigidity were both of practically satisfactorylevels.

Comparative Example 13

A cup-like container with a flange was otained by being molded in thesame manner as in Example 19 except that the plug was of a shape withoutthe bead shape between the flange portion and the stacking portion.

Portions where the cup-like container was measured for its size were asshown in FIG. 32, the molding tools that were used were the same asthose in Examples 18 and 19 but without having a recessed portion forforming the bead, and the portions where the molding tools were measuredfor their sizes were as shown in FIG. 45. The sizes and evaluatedresults were as shown in Table 5. Neither the stacking performance northe rigidity was of practically satisfactory level.

Table 5 TABLE 5 Item Example 18 Example 19 Comp. Ex. 13 Materialstarting material PET PET PET form perform sheet sheet Cup-moldingmethod stretching plug with bead plug with bead plug without is insertedis inserted bead is inserted heat-set blowing into female moldcooling/shaping shrink back onto plug Sizes of tools/perform plug outerdiameter (mm) 60.00 60.00 60.00 outer diameter of bead (mm) 59.20 59.20— outer diameter of stack (mm) 60.00 60.00 60.00 perform inner diameterof mouth of perform (mm) 60.70 — — LFM inner diameter of LFM 61.50 61.5061.50 Sizes of cup thickness (mm) 0.40 0.40 0.40 inner diameter of mouth(D1) (mm) 60.70 60.70 60.70 inner diameter of bead (D4) (mm) 58.90 58.90— outer diameter of stack (D2) (mm) 60.50 60.50 60.50 Evaluation ofperformance stacking performance overlapping amount; +0.5 or more (mm)◯(+0.8) ◯(+0.8) X(−0.2) stack falling test; must be separated ◯ ◯ Xrigidity 20% transverse load (N) ◯ ◯ X

INDUSTRIAL APPLICABILITY

According to the present invention, a sheet provided with at least alayer of an ethylene terephthalate polyester is subjected to theplug-assisted compressed-air or vacuum molding at a particular sheettemperature, at a particular plug temperature or at a particular metalmold temperature by using a plug having a particular shape, making itpossible to produce a heat-molded container having particularorientation profile properties, i.e., in which the biaxial orientationis preferentially taking place in the lower part of the barrel portion.This container exhibits excellent heat resistance and excellent impactstrength in combination, and is useful for containing a content while itis hot.

According to the present invention, further, there is produced athermoplastic resin container having excellent resistance againstdeformation caused by heat and excellent strength by molding athermoplastic resin sheet into the shape of a female mold heated at atemperature higher than the crystallization temperature of the resin byutilizing the compressed air, heat-setting the molded article and, then,reducing the pressure in the molded article to shrink the molded articleinto the shape of a plug which has the shape of a final container toimpart the shape thereto, followed by cooling.

According to the preparation method of the present invention, thefunctions are separated into heat-setting by the female mold and coolingby the plug, contributing to shorten the time for occupying the metalmold and, hence, offering an advantage of enhancing the productivity.The container molded from the thermoplastic polyester sheet has a novelcrystallinity profile in that the side wall of the container is orientedand crystallized, and the side wall has a crystallinity which is higheron the side of the outer surface than on the side of the inner surface,exhibiting excellent heat resistance, impact resistance and appearance.

According to the present invention, further, pre-molded article obtainedby solid-phase-molding a sheet provided with an amorphous thermoplasticpolyester layer is heat-shrunk to obtain an intermediate article whichis, then, molded with the compressed air in a female mold for finalmolding heated at a temperature higher than the crystallization starttemperature of the polyester and is heat-set, and the pressure in theinterior of the molded article is reduced, so that the molded articleshrinks along the outer surface of the plug having the shape of a finalcontainer, to impart the shape thereto, followed by cooling. Therefore,there is obtained a sheet-molded container having excellent heatresistance, impact resistance and transparency not only in the side wallof the container but also at the center in the bottom portion of thecontainer, despite the container is formed by molding an unoriented oramorphous thermoplastic polyester sheet. According to the preparationmethod of the present invention, the functions are separated intoheat-setting by the female mold and cooling by the plug, contributing toshorten the time for occupying the metal mold and, hence, offering anadvantage of enhancing the productivity.

The present invention further makes it possible to obtain, in anastonishing combination, an excellent heat resistance stemming from thecrystallinity of the thermoplastic polyester of not smaller than 15% inthe bottom portion of the container, to obtain excellent impactresistance stemming from a distinguished diffraction peak on the surfaceof an index of a plane (010) in the X-ray diffraction, and to obtain asubstantial transparency in the bottom portion of the container, despitethe container is formed by heat-molding a thermoplastic polyester sheet.

According to the cup-like container having excellent stackingperformance of the present invention, a bead portion is formed over thestacking portion to protrude inward of the container. In the stackedstate, the stacking portion of the upper container is placed on the beadportion of the lower container increasing the overlapping amount at thestacking portion. Even when a plurality of containers are stacked,therefore, the lower containers support the upper containers maintainingstability. Therefore, the upper containers are not depressed beyond thestacking position. The upper and lower containers can be easilyseparated when they are to be used, and markedly improved stackingperformance is obtained.

With the bead being formed on the barrel of the container, further, thecup-like container exhibits improved mechanical strength.

Further, the increased mechanical strength makes it possible to decreasethe thickness of the portion from the flange portion up to the stackingportion.

Further, since the cup is stacked at the stacking portion on the beadportion formed at a position lower than the flange portion, theoverlapping amount increases between the upper container and the lowercontainer in the axial direction as compared to the conventionalcup-like containers that are stacked at the flange portion and at thestacking portion. Therefore, a plurality of containers can be compactlystacked offering great advantages from the standpoint of storage andtransporation.

According to the method of producing the cup-like container with aflange of the invention, the stacking portion and the bead portion havebeen shaped by the shrinking back onto the male plug in the step ofheat-molding and can, hence, be efficiently molded. Moreover, thepreform on which the flange portion has been formed in advance can besubjected to the heat-molding to increase the yield of material.

Further, the preform or the sheet which is a molding precursor used forthe heat-molding may be crystallized or thickened at the flange portionin the case of the preform, or can be crystallized at a portion thatbecomes the flange portion in the case of the sheet prior to beingsubjected to the heat-molding. This makes it possible to provide acup-like container featuring very excellent heat resistance and impactresistance over the whole container inclusive of the flange portion.

1. A method of producing a heat resistant resin container by molding athermoplastic resin sheet by using the compressed air into the shape ofa female mold that is heated at a temperature not lower than thecrystallization temperature of said resin followed by heat-setting, andreducing the pressure in the molded article so as to shrink into theshape of a plug having the shape of a final container to impart theshape thereto, followed by cooling.
 2. A method of producing a heatresistant resin container according to claim 1, wherein a primary moldedarticle obtained by stretching a thermoplastic resin sheet by using theplug, is molded with the compressed air.
 3. A method of producing a heatresistant resin container according to claim 1, wherein thethermoplastic resin sheet is an amorphous sheet of a thermoplasticpolyester.
 4. A method of producing a heat resistant resin containeraccording to claim 1, wherein the surface area of the plug is notsmaller than 3 times as great as the to-be-molded area of thethermoplastic resin sheet.
 5. A method of producing a heat resistantresin container according to claim 1, wherein the temperature of theplug is not lower than a glass transition point of the thermoplasticresin but is not higher than the temperature of the female mold.
 6. Amethod of producing a heat resistant resin container according to claim1, wherein a primary molded article obtained by stretching said sheet byusing a stretching rod, is molded with the compressed air.
 7. A methodof producing a heat resistant resin container according to claim 6,wherein the molding temperature of the plug is from near roomtemperature up to not higher than the crystallization initiatingtemperature of the thermoplastic resin.
 8. A method of producing a heatresistant resin container according to claim 1, wherein said sheet hasbeen shaped in advance so as to form a main heat-molding portion and aflange portion.
 9. A method of producing a heat resistant resincontainer according to claim 1, wherein said sheet is clamped by a jigso that a portion that becomes the flange portion is crystallized.
 10. Amethod of producing a heat resistant resin container according to claim9, wherein said flange portion is thickened or crystallized.
 11. Amethod of producing a heat resistant resin container according to claim1, wherein said plug has a shape capable of forming, on the container, abead portion that protrudes inward of the container and a stackingportion positioned under said bead portion at positions corresponding tothe barrel of the container.
 12. A heat-resistant cup-like containerhaving a flange portion molded by the production method of claim 11,wherein the barrel of said cup-like container is forming a bead portionprotruding inward of the container and a stacking porition positionedunder said bead portion.
 13. A heat-resistant cup-like containeraccording to claim 12, wherein said bead is formed entirely or beingdivied into a plurality of portions along the circumferential directionof the barrel.